A topological space is semilocally simply connected (also called semilocally 1-connected)
if every point
has a neighborhood
such that any loop
with basepoint
is homotopic to the trivial
loop. The prefix semi- refers to the fact that the homotopy
which takes
to the trivial loop can leave
and travel to other parts of
.
The property of semilocal simple connectedness is important because it is a necessary and sufficient condition for a connected, locally pathwise-connected space to have a universal cover.