* Hendecagon: A polygon with eleven sides.
* Hendecahedron: A polyhedron with eleven faces.
* Hendecasyllabic: Having eleven syllables (e.g., a hendecasyllabic line of poetry).
While less common, you might also encounter:
* Hendecamer: A group of eleven.
* Hendecanal: A chemical compound with eleven carbon atoms.
These words are not as frequently used as others with Greek numerical prefixes, but they exist in specialized vocabulary.