An eleven sided shape is called a hendecagon.
hendecagon
hendecagon
Two-dimensional: Pentagon Three-dimensional: Pentahedron
It is a hendecagon.
hendecagon
hendecagon
The name of an eleven sided geometric shape is a Hendecagon or endecagon.
It is called a hendecagon or, less often, an endecagon.
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It is a Hendecagon (or endecagon).
A two-dimensional eleven-sided figure is called a hendecagon.