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A set $S$ is simply connected if and only if for every path $p$ with image in $S$ and every point $a \in S$, the path $p$ is homotopic to the constant path at $a$ in $S$.
A set $S$ is simply connected if and only if it is path connected and every loop in $S$ is homotopic to a constant loop.
A set $S$ is simply connected if and only if $S$ is empty or there exists a point $a \in S$ such that for every loop $p$ in $S$ with $p(0) = p(1) = a$, $p$ is homotopic to the constant loop at $a$.
A set $S$ is simply connected if and only if it is path connected and every path in $S$ with the same start and end point is homotopic to a constant path.
A set $S$ is simply connected if and only if it is path connected and any two paths with the same endpoints are homotopic.
The product of two simply connected sets is simply connected.
If $S$ is contractible, then $S$ is simply connected.
If a set is contractible, then it is connected.
If $S$ is contractible, then $S$ is path-connected.
If $f: S \to T$ and $g: T \to U$ are continuous maps, and $T$ is contractible, then $g \circ f$ is nullhomotopic.
If $f$ is a continuous map from $S$ to $T$ and $T$ is contractible, then $f$ is nullhomotopic.
If $S$ is contractible and $f: S \to T$ is continuous, then $f$ is nullhomotopic.
If $f_1$ and $f_2$ are continuous maps from $S$ to $T$, and $g_1$ and $g_2$ are continuous maps from $T$ to $U$, and $T$ is contractible and $U$ is path-connected, then $g_1 \circ f_1$ and $g_2 \circ f_2$ are homotopic.
If $f$ and $g$ are continuous maps from $S$ to $T$, where $T$ is contractible, then $f$ and $g$ are homotopic.
If $S$ is contractible and $T$ is path-connected, then any two continuous maps from $S$ to $T$ are homotopic.
The whole complex plane is starlike.
If $S$ is a nonempty convex set, then $S$ is starlike.
If $S$ is a nonempty convex set and $T$ is a set such that the relative interior of $S$ is a subset of $T$ and $T$ is a subset of the closure of $S$, then $T$ is starlike.
If $S$ is a starlike set, then $S$ is contractible.
If $S$ is a starlike set, then $S$ is contractible.
The whole space $\mathbb{R}^n$ is contractible.
If $S$ is starlike, then $S$ is simply connected.
Any convex set is simply connected.
If $S$ is starlike, then $S$ is path-connected.
Any starlike set is connected.
A set $S$ is an interval if and only if it is simply connected.
The empty space is contractible.
If $S$ is a convex set and $T$ is a subset of $S$ that contains the relative interior of $S$ and is contained in the closure of $S$, then $T$ is contractible.
Any convex set is contractible.
The singleton set $\{a\}$ is contractible.
A real interval is contractible.
If $S$ and $T$ are contractible sets, then $S \times T$ is contractible.
If for every open set $w$ and every point $x$ in $w$, there exists an open set $u$ containing $x$ and a set $v$ such that $P(v)$ holds and $u \subseteq v \subseteq w$, then $P$ holds locally on $S$.
If $S$ is locally $P$, then for any open set $w$ in $S$ and any point $x$ in $w$, there exists an open set $u$ in $S$ containing $x$ and a set $v$ containing $u$ such that $v$ is contained in $w$ and $v$ is $P$.
If $S$ is locally $P$, then $S$ is locally $Q$ whenever $Q$ implies $P$.
If $S$ is locally $P$ and $t$ is an open subset of $S$, then $t$ is locally $P$.
If $S$ is locally $P$ and $t$ is closed in $S$, then $S - t$ is locally $P$.
The empty set is locally empty.
A set is locally $P$ if and only if it is $P$.
A set $S$ is locally $P$ if and only if for every open set $T$ containing a point $x$ of $S$, there exists an open set $U$ containing $x$ such that $S \cap U$ is contained in a set $V$ satisfying $P$ and contained in $S \cap T$.
If $S$ and $T$ are locally $P$, then $S \cap T$ is locally $P$.
If $S$ and $T$ are locally $P$ and $Q$, respectively, then $S \times T$ is locally $R$.
If $f$ is a homeomorphism from a locally $P$ space $S$ to a space $T$, and if $Q$ is a property such that whenever $S$ is a $P$ space and $f$ is a homeomorphism from $S$ to $S'$, then $S'$ has property $Q$, then $T$ has property $Q$.
If $f$ is a homeomorphism between $S$ and $T$, and $P$ and $Q$ are properties of topological spaces such that $S$ has property $P$ if and only if $T$ has property $Q$, then $S$ is locally $P$ if and only if $T$ is locally $Q$.
If $S$ and $T$ are homeomorphic, then $S$ is locally $P$ if and only if $T$ is locally $Q$.
If two topological spaces are homeomorphic, then they are locally compact if and only if the other is locally compact.
If $P$ is a property of sets that is invariant under translations, then the property of being locally $P$ is also invariant under translations.
If $f$ is a linear map from $\mathbb{R}^n$ to $\mathbb{R}^m$ that is injective, then $f$ is a local homeomorphism.
If $f$ is a continuous map from a topological space $S$ to a topological space $T$, and if $f$ maps open sets in $S$ to open sets in $T$, then $f$ is an open map.
If $S$ is a connected set, $P$ and $Q$ are properties of points of $S$, and $a$ and $b$ are points of $S$ such that $P$ holds for $a$ and $b$ and $Q$ holds for $a$, then $Q$ holds for $b$.
If $S$ is a connected set, $a, b \in S$, $P(a)$ and $P(b)$ are true, and $R$ is a relation on $S$ that is transitive, symmetric, and reflexive, then $R(a, b)$ is true.
Suppose $S$ is a connected set and $P$ is a property that holds for $a \in S$. If $P$ is preserved by open neighborhoods, then $P$ holds for all $b \in S$.
If $S$ is a connected set and $R$ is a symmetric and transitive relation on $S$ such that for every $a \in S$, there exists an open set $T$ containing $a$ such that $R$ holds for every pair of points in $T$, then $R$ holds for every pair of points in $S$.
If $f$ is locally constant on a connected set $S$, then $f$ is constant on $S$.
If $S$ is connected, then $f$ is locally constant on $S$ if and only if $f$ is constant on $S$.
A set $S$ is locally compact if and only if for every $x \in S$, there exist open sets $U$ and $V$ such that $x \in U \subseteq V \subseteq S$ and $U$ and $V$ are compact.
If $S$ is a locally compact set, then for every $x \in S$, there exist an open set $u$ containing $x$ and a compact set $v$ containing $u$ such that $v \subseteq S$.
A topological space $S$ is locally compact if and only if for every $x \in S$, there exists an open set $U$ containing $x$ such that $U$ is compact and contained in $S$.
A topological space $X$ is locally compact if and only if for every $x \in X$, there exists an open ball $B(x, \epsilon)$ such that $B(x, \epsilon) \cap X$ is closed.
A set $S$ is locally compact if and only if for every compact subset $K$ of $S$, there exist open subsets $U$ and $V$ of $S$ such that $K \subseteq U \subseteq V \subseteq S$ and $V$ is compact.
Any open set is locally compact.
If $S$ is a closed set, then $S$ is locally compact.
The set of all real numbers is locally compact.
If $S$ and $t$ are locally compact, then $S \cap t$ is locally compact.
If $t$ is a closed subset of a locally compact set $S$, then $t$ is locally compact.
If $S$ is a locally compact space, then $S - \{a\}$ is also locally compact.
A set $S$ is locally closed if and only if it is locally compact.
If $S$ and $T$ are locally compact, and $S$ and $T$ are open in $S \cup T$, then $S \cup T$ is locally compact.
If $S$ and $T$ are locally compact and closed in $S \cup T$, then $S \cup T$ is locally compact.
If $S$ and $T$ are locally compact, then $S \times T$ is locally compact.
A topological space is locally compact if and only if every compact subset of it is contained in an open subset of it that is also compact.
If $S$ is a compact set and $C$ is a component of $S$, then $C$ is the intersection of all open and closed subsets of $S$ that contain $C$.
If $C$ is a compact component of a locally compact set $S$, then there exists a compact open set $K$ such that $C \subseteq K \subseteq U$.
Suppose $S$ is a locally compact set, $C$ is a component of $S$, and $C$ is compact. Then there exists a compact open set $K$ such that $C \subseteq K \subseteq U$.
If $S$ is a locally compact set, $C$ is a component of $S$, and $C$ is compact, then $C$ is the intersection of all compact open sets containing $C$.
If every point in a topological space has a connected neighborhood, then the space is locally connected.
If $S$ is locally connected and $t$ is an open subset of $S$, then the connected component of $t$ containing $x$ is open in $S$.
If $S$ is a topological space and $v$ is an open subset of $S$, then for every $x \in v$, there exists an open connected subset $u$ of $S$ such that $x \in u \subseteq v$.
A topological space $S$ is locally connected if and only if for every open set $v$ containing a point $x$, there exists an open set $u$ containing $x$ such that $u$ is connected and $u \subseteq v$.
A topological space is locally connected if and only if every point in every open set is contained in an open connected set.
If every point in $S$ has a neighborhood that is path-connected, then $S$ is locally path-connected.
If $S$ is locally path-connected and $t$ is an open subset of $S$, then the path-component of $x$ in $t$ is open in $S$.
If $S$ is locally path-connected, then for every open set $v$ and every point $x \in v$, there exists an open set $u$ such that $x \in u \subseteq v$ and $u$ is path-connected.
A topological space $S$ is locally path-connected if and only if for every open set $V$ containing a point $x$, there exists an open set $U$ containing $x$ such that $U$ is path-connected and $U \subseteq V$.
A topological space is locally path-connected if and only if every point has an open path-connected neighborhood.
A topological space is locally connected if and only if every component of every open subset is open.
A topological space is locally connected if and only if for every open set $U$ and every point $x \in U$, there exists an open set $V$ such that $x \in V \subseteq U$ and for every $y \in V$, there exists a connected set $C$ such that $x, y \in C \subseteq U$.
A topological space is locally path-connected if and only if for every point $x$ and every open neighborhood $V$ of $x$, there exists an open neighborhood $U$ of $x$ such that for every point $y$ in $U$, there exists a path from $x$ to $y$ whose image is contained in $V$.
If every point in a space $S$ has a neighborhood that is path-connected, then every point in $S$ has a neighborhood that is connected.
If $S$ is a locally connected space and $c$ is a component of $S$, then $c$ is locally connected.
If $S$ is locally path-connected and $c$ is a component of $S$, then $c$ is locally path-connected.
If $S$ is locally path-connected, then the connected component of $S$ containing $x$ is also locally path-connected.
Any open set is locally path-connected.
Any open set is locally connected.
The real vector space $\mathbb{R}^n$ is locally path-connected.
The real line is locally connected.
If $S$ is locally connected, then the connected component of $S$ containing $x$ is open in $S$.
If $S$ is locally connected and $c$ is a component of $S$, then $c$ is open in $S$.
If $S$ is locally path-connected, then the path-component of $x$ in $S$ is open in $S$.
If $S$ is locally path-connected, then the path-component of $x$ in $S$ is closed in $S$.