apothem

UK: /ˈæpəˌθɛm/ US: (ap′ə them′)

WordReference Random House Unabridged Dictionary of American English © 2025

ap•o•them  (ap′ə them′), n. [Geom.]

1. Mathematics a perpendicular from the center of a regular polygon to one of its sides.

• French apothème, probably on the model of Greek hypóthēma base; see apo-, theme
• 1855–60

Collins Concise English Dictionary © HarperCollins Publishers::

apothem / ˈæpəˌθɛm/ noun

1. the perpendicular line or distance from the centre of a regular polygon to any of its sides

Etymology: 20th Century: from apo- + Greek thema, from tithenai to place