wikilangs/sr

Serbian - Wikilangs Models

Comprehensive Research Report & Full Ablation Study

This repository contains NLP models trained and evaluated by Wikilangs, specifically on Serbian Wikipedia data. We analyze tokenizers, n-gram models, Markov chains, vocabulary statistics, and word embeddings.

📋 Repository Contents

Models & Assets

• Tokenizers (8k, 16k, 32k, 64k)
• N-gram models (2, 3, 4, 5-gram)
• Markov chains (context of 1, 2, 3, 4 and 5)
• Subword N-gram and Markov chains
• Embeddings in various sizes and dimensions (aligned and unaligned)
• Language Vocabulary
• Language Statistics

Analysis and Evaluation

• 1. Tokenizer Evaluation
• 2. N-gram Model Evaluation
• 3. Markov Chain Evaluation
• 4. Vocabulary Analysis
• 5. Word Embeddings Evaluation
• 6. Morphological Analysis (Experimental)
• 7. Summary & Recommendations
• Metrics Glossary
• Visualizations Index

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1. Tokenizer Evaluation

Results

Vocab Size	Compression	Avg Token Len	UNK Rate	Total Tokens
8k	3.437x	3.44	0.0903%	3,193,783
16k	3.819x	3.82	0.1004%	2,874,429
32k	4.168x	4.17	0.1095%	2,633,814
64k	4.463x 🏆	4.46	0.1173%	2,459,404

Tokenization Examples

Below are sample sentences tokenized with each vocabulary size:

Sample 1: Сабо () је веома често мађарско презиме као на пример код Срба Јовановић, Николи...

Vocab	Tokens	Count
8k	▁сабо ▁() ▁је ▁веома ▁често ▁мађар ско ▁презиме ▁као ▁на ... (+22 more)	32
16k	▁сабо ▁() ▁је ▁веома ▁често ▁мађарско ▁презиме ▁као ▁на ▁пример ... (+17 more)	27
32k	▁сабо ▁() ▁је ▁веома ▁често ▁мађарско ▁презиме ▁као ▁на ▁пример ... (+17 more)	27
64k	▁сабо ▁() ▁је ▁веома ▁често ▁мађарско ▁презиме ▁као ▁на ▁пример ... (+17 more)	27

Sample 2: Еребус се може односити на: Еребус, божанство из грчке митологије планину на Ант...

Vocab	Tokens	Count
8k	▁ере бу с ▁се ▁може ▁односити ▁на : ▁ере бу ... (+29 more)	39
16k	▁ере бус ▁се ▁може ▁односити ▁на : ▁ере бус , ... (+22 more)	32
32k	▁ере бус ▁се ▁може ▁односити ▁на : ▁ере бус , ... (+17 more)	27
64k	▁ере бус ▁се ▁може ▁односити ▁на : ▁ере бус , ... (+17 more)	27

Sample 3: Ово је страница за вишезначну одредницу појма Лимбо. Лимбо (програмски језик) Ли...

Vocab	Tokens	Count
8k	▁ово ▁је ▁страница ▁за ▁више зна чну ▁одре дни цу ... (+27 more)	37
16k	▁ово ▁је ▁страница ▁за ▁више зна чну ▁одре дни цу ... (+26 more)	36
32k	▁ово ▁је ▁страница ▁за ▁више зна чну ▁одре дницу ▁појма ... (+22 more)	32
64k	▁ово ▁је ▁страница ▁за ▁вишезна чну ▁одре дницу ▁појма ▁лимбо ... (+15 more)	25

Key Findings

• Best Compression: 64k achieves 4.463x compression
• Lowest UNK Rate: 8k with 0.0903% unknown tokens
• Trade-off: Larger vocabularies improve compression but increase model size
• Recommendation: 32k vocabulary provides optimal balance for production use

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2. N-gram Model Evaluation

Results

N-gram	Variant	Perplexity	Entropy	Unique N-grams	Top-100 Coverage	Top-1000 Coverage
2-gram	Word	101,010	16.62	541,740	10.5%	23.1%
2-gram	Subword	417 🏆	8.70	10,655	57.4%	97.8%
3-gram	Word	173,243	17.40	753,336	12.1%	19.9%
3-gram	Subword	3,794	11.89	91,805	20.7%	60.8%
4-gram	Word	303,317	18.21	1,236,985	12.9%	18.9%
4-gram	Subword	23,753	14.54	568,494	8.7%	30.0%
5-gram	Word	175,057	17.42	859,857	15.7%	23.0%
5-gram	Subword	103,293	16.66	1,934,363	4.2%	16.6%

Top 5 N-grams by Size

2-grams (Word):

Rank	N-gram	Count
1	да се	37,569
2	да је	37,093
3	који је	32,864
4	је у	32,694
5	у француској	28,666

3-grams (Word):

Rank	N-gram	Count
1	референце спољашње везе	17,332
2	географија насеља у	14,556
3	из године у	12,667
4	подацима из године	12,386
5	по подацима из	12,385

4-grams (Word):

Rank	N-gram	Count
1	географија насеља у француској	12,290
2	у француској географија насеља	12,231
3	француској географија насеља у	12,231
4	по подацима из године	12,218
5	у општини је живело	12,073

5-grams (Word):

Rank	N-gram	Count
1	француској географија насеља у француској	12,231
2	у француској географија насеља у	12,231
3	а густина насељености је износила	12,019
4	године у општини је живело	12,013
5	по подацима из године у	12,009

2-grams (Subword):

Rank	N-gram	Count
1	а _	4,254,775
2	е _	3,484,880
3	и _	2,798,461
4	_ с	2,402,734
5	_ п	2,167,464

3-grams (Subword):

Rank	N-gram	Count
1	ј е _	1,227,613
2	_ ј е	1,007,997
3	_ н а	904,776
4	_ п о	898,886
5	н а _	849,756

4-grams (Subword):

Rank	N-gram	Count
1	_ ј е _	832,365
2	_ н а _	351,709
3	_ с е _	341,716
4	, _ - {	333,041
5	_ с у _	265,965

5-grams (Subword):

Rank	N-gram	Count
1	а _ ј е _	233,666
2	_ г о д и	196,626
3	г о д и н	193,637
4	о _ ј е _	179,487
5	о д и н е	149,943

Key Findings

• Best Perplexity: 2-gram (subword) with 417
• Entropy Trend: Decreases with larger n-grams (more predictable)
• Coverage: Top-1000 patterns cover ~17% of corpus
• Recommendation: 4-gram or 5-gram for best predictive performance

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3. Markov Chain Evaluation

Results

Context	Variant	Avg Entropy	Perplexity	Branching Factor	Unique Contexts	Predictability
1	Word	1.0281	2.039	9.57	1,005,421	0.0%
1	Subword	0.9082	1.877	7.42	4,016	9.2%
2	Word	0.2993	1.231	1.87	9,615,248	70.1%
2	Subword	0.9001	1.866	6.18	29,746	10.0%
3	Word	0.1002	1.072	1.20	17,985,483	90.0%
3	Subword	0.8701	1.828	4.99	183,681	13.0%
4	Word	0.0325 🏆	1.023	1.05	21,482,040	96.7%
4	Subword	0.7815	1.719	3.70	916,341	21.8%

Generated Text Samples (Word-based)

Below are text samples generated from each word-based Markov chain model:

Context Size 1:

1. је само састављали збирке одељења за члана председништва цк кпј у уметничко друштво је русија је
2. у овом делу sidereus nuncius године националност срби плаћали променила велики рептили који вређа кр...
3. и најавни део провансе и након што су поставили војску је 404 метара максималној 634 године

Context Size 2:

1. да се никада не напушта ни наду децу треба научити до 6 маја по црквеном а 6
2. да је основна обрада добро изведена и претежно сува са највећим избором литературе са исказима свјед...
3. који је стекао и велики број лоше васпитане деце из брака са марином севером и игра финале

Context Size 3:

1. референце спољашње везе база података insee арбукав на страници националног географског института фр...
2. географија насеља у француској север у француској географија насеља у француској мозел у француској ...
3. из године у општини је живело 41 становника а густина насељености је износила 37 47 општина се прост...

Context Size 4:

1. француској географија насеља у француској аверон у француској географија насеља у француској север у...
2. у француској географија насеља у француској алије у француској географија насеља у француској арјеж ...
3. по подацима из године у општини је живело становника а густина насељености је износила 148 84 општин...

Generated Text Samples (Subword-based)

Below are text samples generated from each subword-based Markov chain model:

Context Size 1:

1. _хе_фенсјутрават
2. а_рин-{cetote,_с
3. и,_ка_овезе_е_".

Context Size 2:

1. а_18._евојмаљивин
2. е_се_дембрановод_
3. и_мрепрата_и_ствр

Context Size 3:

1. је_у_бела_милазе_м
2. _је_(трна_тесаветс
3. _на_са_редињени_од

Context Size 4:

1. _је_насељености_чиј
2. _на_светом,_и_мишље
3. _се_раку.потребљено

Key Findings

• Best Predictability: Context-4 (word) with 96.7% predictability
• Branching Factor: Decreases with context size (more deterministic)
• Memory Trade-off: Larger contexts require more storage (916,341 contexts)
• Recommendation: Context-3 or Context-4 for text generation

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4. Vocabulary Analysis

Statistics

Metric	Value
Vocabulary Size	517,888
Total Tokens	24,596,294
Mean Frequency	47.49
Median Frequency	4
Frequency Std Dev	2239.63

Most Common Words

Rank	Word	Frequency
1	је	841,603
2	у	779,149
3	и	778,274
4	на	355,146
5	се	345,085
6	су	272,433
7	да	243,646
8	од	217,292
9	за	179,897
10	са	153,021

Least Common Words (from vocabulary)

Rank	Word	Frequency
1	astropixels	2
2	astron	2
3	periodicities	2
4	tjeenk	2
5	morsels	2
6	heatseekers	2
7	млађака	2
8	espenak	2
9	пба	2
10	пбка	2

Zipf's Law Analysis

Metric	Value
Zipf Coefficient	0.9204
R² (Goodness of Fit)	0.998749
Adherence Quality	excellent

Coverage Analysis

Top N Words	Coverage
Top 100	29.3%
Top 1,000	48.4%
Top 5,000	64.3%
Top 10,000	71.6%

Key Findings

• Zipf Compliance: R²=0.9987 indicates excellent adherence to Zipf's law
• High Frequency Dominance: Top 100 words cover 29.3% of corpus
• Long Tail: 507,888 words needed for remaining 28.4% coverage

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5. Word Embeddings Evaluation

5.1 Cross-Lingual Alignment

5.2 Model Comparison

Model	Dimension	Isotropy	Semantic Density	Alignment R@1	Alignment R@10
mono_32d	32	0.7304	0.4041	N/A	N/A
mono_64d	64	0.6931	0.3311	N/A	N/A
mono_128d	128	0.6524	0.2382	N/A	N/A
aligned_32d	32	0.7304 🏆	0.4084	0.0400	0.2700
aligned_64d	64	0.6931	0.3210	0.1200	0.4240
aligned_128d	128	0.6524	0.2421	0.1280	0.4500

Key Findings

• Best Isotropy: aligned_32d with 0.7304 (more uniform distribution)
• Semantic Density: Average pairwise similarity of 0.3242. Lower values indicate better semantic separation.
• Alignment Quality: Aligned models achieve up to 12.8% R@1 in cross-lingual retrieval.
• Recommendation: 128d aligned for best cross-lingual performance

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6. Morphological Analysis (Experimental)

This section presents an automated morphological analysis derived from the statistical divergence between word-level and subword-level models. By analyzing where subword predictability spikes and where word-level coverage fails, we can infer linguistic structures without supervised data.

6.1 Productivity & Complexity

Metric	Value	Interpretation	Recommendation
Productivity Index	5.000	High morphological productivity	Reliable analysis
Idiomaticity Gap	0.390	High formulaic/idiomatic content	-

6.2 Affix Inventory (Productive Units)

These are the most productive prefixes and suffixes identified by sampling the vocabulary for global substitutability patterns. A unit is considered an affix if stripping it leaves a valid stem that appears in other contexts.

Productive Prefixes

Prefix	Examples
-s	schiffer, slotove, saposchnikowii
-с	сеља, сажела, социјалиста
-a	amonijak, abnormal, amundsen
-к	корисника, квасци, конвективну
-а	анализатори, алентаун, атеници
-ма	марашли, мауретаније, маленченко
-по	поморишки, подстрекивани, покајањем
-b	base, berlencourt, bessins

Productive Suffixes

Suffix	Examples
-а	екосистемска, дикава, пауза
-s	entomopisthius, walkers, knottnerus
-a	taeniifera, jouvea, pillaia
-и	марашли, темперовани, анализатори
-е	пасуљанске, ларе, мауретаније
-us	entomopisthius, knottnerus, ovigerus
-м	деутеријумом, фруктозом, истакнутим
-у	упу, досежу, бубну

6.3 Bound Stems (Lexical Roots)

Bound stems are high-frequency subword units that are semantically cohesive but rarely appear as standalone words. These often correspond to the 'core' of a word that requires inflection or derivation to be valid.

Stem	Cohesion	Substitutability	Examples
ости	1.98x	208 contexts	рости, аости, остин
ском	2.03x	155 contexts	уском, еском, воском
ност	2.07x	99 contexts	ностра, ностер, иностр
анск	1.44x	640 contexts	данск, канск, јански
нски	1.73x	187 contexts	јански, шонски, сенски
асељ	2.49x	36 contexts	насељу, насеље, засеље
општ	1.98x	83 contexts	опште, општу, општи
држа	1.66x	187 contexts	држао, држач, одржа
егов	1.78x	120 contexts	његов, негов, бегов
ациј	1.66x	153 contexts	лациј, ација, нације
пшти	2.16x	38 contexts	општи, уопшти, општио
ориј	1.50x	191 contexts	орија, морији, морије

6.4 Affix Compatibility (Co-occurrence)

This table shows which prefixes and suffixes most frequently co-occur on the same stems, revealing the 'stacking' rules of the language's morphology.

Prefix	Suffix	Frequency	Examples
-с	-а	93 words	светила, сенахирима
-a	-s	89 words	avidus, abiskoensis
-к	-а	84 words	капитализација, краварица
-s	-s	79 words	spretus, synechogobius
-a	-a	61 words	albopicta, anamaera
-с	-и	56 words	сокобањи, сасечени
-с	-е	54 words	стручне, смртнице
-а	-а	52 words	ангажманима, астрофизичка
-с	-м	51 words	сопством, севиљском
-к	-и	49 words	касноантички, карантанији

6.5 Recursive Morpheme Segmentation

Using Recursive Hierarchical Substitutability, we decompose complex words into their constituent morphemes. This approach handles nested affixes (e.g., prefix-prefix-root-suffix).

Word	Suggested Split	Confidence	Stem
електрана	електр-а-на	7.5	а
одгурнути	одгурн-у-ти	7.5	у
областимаи	области-ма-и	7.5	ма
оправдани	оправд-а-ни	7.5	а
меканском	ме-канск-ом	6.0	канск
поштовану	пошто-ва-ну	6.0	пошто
јованкину	јован-ки-ну	6.0	јован
коминикеи	комини-ке-и	6.0	комини
проживети	пр-оживе-ти	6.0	оживе
катаринин	катари-ни-н	6.0	катари
примењену	приме-ње-ну	6.0	приме
фосфолипида	фосфолипид-а	4.5	фосфолипид
зеведејева	зеведејев-а	4.5	зеведејев
радиоактивности	радиоактивност-и	4.5	радиоактивност
скорпиона	скорпион-а	4.5	скорпион

6.6 Linguistic Interpretation

Automated Insight: The language Serbian shows high morphological productivity. The subword models are significantly more efficient than word models, suggesting a rich system of affixation or compounding.

Note on Idiomaticity: The high Idiomaticity Gap suggests a large number of frequent multi-word expressions or formulaic sequences that are statistically distinct from their component parts.

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7. Summary & Recommendations

Production Recommendations

Component	Recommended	Rationale
Tokenizer	64k BPE	Best compression (4.46x)
N-gram	2-gram	Lowest perplexity (417)
Markov	Context-4	Highest predictability (96.7%)
Embeddings	100d	Balanced semantic capture and isotropy

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Appendix: Metrics Glossary & Interpretation Guide

This section provides definitions, intuitions, and guidance for interpreting the metrics used throughout this report.

Tokenizer Metrics

Compression Ratio

Definition: The ratio of characters to tokens (chars/token). Measures how efficiently the tokenizer represents text.

Intuition: Higher compression means fewer tokens needed to represent the same text, reducing sequence lengths for downstream models. A 3x compression means ~3 characters per token on average.

What to seek: Higher is generally better for efficiency, but extremely high compression may indicate overly aggressive merging that loses morphological information.

Average Token Length (Fertility)

Definition: Mean number of characters per token produced by the tokenizer.

Intuition: Reflects the granularity of tokenization. Longer tokens capture more context but may struggle with rare words; shorter tokens are more flexible but increase sequence length.

What to seek: Balance between 2-5 characters for most languages. Arabic/morphologically-rich languages may benefit from slightly longer tokens.

Unknown Token Rate (OOV Rate)

Definition: Percentage of tokens that map to the unknown/UNK token, indicating words the tokenizer cannot represent.

Intuition: Lower OOV means better vocabulary coverage. High OOV indicates the tokenizer encounters many unseen character sequences.

What to seek: Below 1% is excellent; below 5% is acceptable. BPE tokenizers typically achieve very low OOV due to subword fallback.

N-gram Model Metrics

Perplexity

Definition: Measures how "surprised" the model is by test data. Mathematically: 2^(cross-entropy). Lower values indicate better prediction.

Intuition: If perplexity is 100, the model is as uncertain as if choosing uniformly among 100 options at each step. A perplexity of 10 means effectively choosing among 10 equally likely options.

What to seek: Lower is better. Perplexity decreases with larger n-grams (more context). Values vary widely by language and corpus size.

Entropy

Definition: Average information content (in bits) needed to encode the next token given the context. Related to perplexity: perplexity = 2^entropy.

Intuition: High entropy means high uncertainty/randomness; low entropy means predictable patterns. Natural language typically has entropy between 1-4 bits per character.

What to seek: Lower entropy indicates more predictable text patterns. Entropy should decrease as n-gram size increases.

Coverage (Top-K)

Definition: Percentage of corpus occurrences explained by the top K most frequent n-grams.

Intuition: High coverage with few patterns indicates repetitive/formulaic text; low coverage suggests diverse vocabulary usage.

What to seek: Depends on use case. For language modeling, moderate coverage (40-60% with top-1000) is typical for natural text.

Markov Chain Metrics

Average Entropy

Definition: Mean entropy across all contexts, measuring average uncertainty in next-word prediction.

Intuition: Lower entropy means the model is more confident about what comes next. Context-1 has high entropy (many possible next words); Context-4 has low entropy (few likely continuations).

What to seek: Decreasing entropy with larger context sizes. Very low entropy (<0.1) indicates highly deterministic transitions.

Branching Factor

Definition: Average number of unique next tokens observed for each context.

Intuition: High branching = many possible continuations (flexible but uncertain); low branching = few options (predictable but potentially repetitive).

What to seek: Branching factor should decrease with context size. Values near 1.0 indicate nearly deterministic chains.

Predictability

Definition: Derived metric: (1 - normalized_entropy) × 100%. Indicates how deterministic the model's predictions are.

Intuition: 100% predictability means the next word is always certain; 0% means completely random. Real text falls between these extremes.

What to seek: Higher predictability for text generation quality, but too high (>98%) may produce repetitive output.

Vocabulary & Zipf's Law Metrics

Zipf's Coefficient

Definition: The slope of the log-log plot of word frequency vs. rank. Zipf's law predicts this should be approximately -1.

Intuition: A coefficient near -1 indicates the corpus follows natural language patterns where a few words are very common and most words are rare.

What to seek: Values between -0.8 and -1.2 indicate healthy natural language distribution. Deviations may suggest domain-specific or artificial text.

R² (Coefficient of Determination)

Definition: Measures how well the linear fit explains the frequency-rank relationship. Ranges from 0 to 1.

Intuition: R² near 1.0 means the data closely follows Zipf's law; lower values indicate deviation from expected word frequency patterns.

What to seek: R² > 0.95 is excellent; > 0.99 indicates near-perfect Zipf adherence typical of large natural corpora.

Vocabulary Coverage

Definition: Cumulative percentage of corpus tokens accounted for by the top N words.

Intuition: Shows how concentrated word usage is. If top-100 words cover 50% of text, the corpus relies heavily on common words.

What to seek: Top-100 covering 30-50% is typical. Higher coverage indicates more repetitive text; lower suggests richer vocabulary.

Word Embedding Metrics

Isotropy

Definition: Measures how uniformly distributed vectors are in the embedding space. Computed as the ratio of minimum to maximum singular values.

Intuition: High isotropy (near 1.0) means vectors spread evenly in all directions; low isotropy means vectors cluster in certain directions, reducing expressiveness.

What to seek: Higher isotropy generally indicates better-quality embeddings. Values > 0.1 are reasonable; > 0.3 is good. Lower-dimensional embeddings tend to have higher isotropy.

Average Norm

Definition: Mean magnitude (L2 norm) of word vectors in the embedding space.

Intuition: Indicates the typical "length" of vectors. Consistent norms suggest stable training; high variance may indicate some words are undertrained.

What to seek: Relatively consistent norms across models. The absolute value matters less than consistency (low std deviation).

Cosine Similarity

Definition: Measures angular similarity between vectors, ranging from -1 (opposite) to 1 (identical direction).

Intuition: Words with similar meanings should have high cosine similarity. This is the standard metric for semantic relatedness in embeddings.

What to seek: Semantically related words should score > 0.5; unrelated words should be near 0. Synonyms often score > 0.7.

t-SNE Visualization

Definition: t-Distributed Stochastic Neighbor Embedding - a dimensionality reduction technique that preserves local structure for visualization.

Intuition: Clusters in t-SNE plots indicate groups of semantically related words. Spread indicates vocabulary diversity; tight clusters suggest semantic coherence.

What to seek: Meaningful clusters (e.g., numbers together, verbs together). Avoid over-interpreting distances - t-SNE preserves local, not global, structure.

General Interpretation Guidelines

1. Compare within model families: Metrics are most meaningful when comparing models of the same type (e.g., 8k vs 64k tokenizer).
2. Consider trade-offs: Better performance on one metric often comes at the cost of another (e.g., compression vs. OOV rate).
3. Context matters: Optimal values depend on downstream tasks. Text generation may prioritize different metrics than classification.
4. Corpus influence: All metrics are influenced by corpus characteristics. Wikipedia text differs from social media or literature.
5. Language-specific patterns: Morphologically rich languages (like Arabic) may show different optimal ranges than analytic languages.

Visualizations Index

Visualization	Description
Tokenizer Compression	Compression ratios by vocabulary size
Tokenizer Fertility	Average token length by vocabulary
Tokenizer OOV	Unknown token rates
Tokenizer Total Tokens	Total tokens by vocabulary
N-gram Perplexity	Perplexity by n-gram size
N-gram Entropy	Entropy by n-gram size
N-gram Coverage	Top pattern coverage
N-gram Unique	Unique n-gram counts
Markov Entropy	Entropy by context size
Markov Branching	Branching factor by context
Markov Contexts	Unique context counts
Zipf's Law	Frequency-rank distribution with fit
Vocab Frequency	Word frequency distribution
Top 20 Words	Most frequent words
Vocab Coverage	Cumulative coverage curve
Embedding Isotropy	Vector space uniformity
Embedding Norms	Vector magnitude distribution
Embedding Similarity	Word similarity heatmap
Nearest Neighbors	Similar words for key terms
t-SNE Words	2D word embedding visualization
t-SNE Sentences	2D sentence embedding visualization
Position Encoding	Encoding method comparison
Model Sizes	Storage requirements
Performance Dashboard	Comprehensive performance overview

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About This Project

Data Source

Models trained on wikipedia-monthly - a monthly snapshot of Wikipedia articles across 300+ languages.

Project

A project by Wikilangs - Open-source NLP models for every Wikipedia language.

Maintainer

Omar Kamali - Omneity Labs

Citation

If you use these models in your research, please cite:

@misc{wikilangs2025,
  author = {Kamali, Omar},
  title = {Wikilangs: Open NLP Models for Wikipedia Languages},
  year = {2025},
  doi = {10.5281/zenodo.18073153},
  publisher = {Zenodo},
  url = {https://huggingface.co/wikilangs}
  institution = {Omneity Labs}
}

License

MIT License - Free for academic and commercial use.

Links

• 🌐 Website: wikilangs.org
• 🤗 Models: huggingface.co/wikilangs
• 📊 Data: wikipedia-monthly
• 👤 Author: Omar Kamali
• 🤝 Sponsor: Featherless AI

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Generated by Wikilangs Models Pipeline

Report Date: 2026-01-11 00:46:21