subtend

UK: /səbˈtɛnd/ US: (səb tend′, sub-)

WordReference Random House Unabridged Dictionary of American English © 2025

sub•tend  (səb tend′, sub-), v.t. 

1. Mathematics [Geom.] to extend under or be opposite to:
   a chord subtending an arc.
2. Botany (of a leaf, bract, etc.) to occur beneath or close to.
3. to form or mark the outline or boundary of.

• Latin subtendere to stretch beneath, equivalent. to sub- sub- + tendere to stretch; see tend¹
• 1560–70

Collins Concise English Dictionary © HarperCollins Publishers::

subtend / səbˈtɛnd/ verb (transitive)

1. to be opposite to and delimit (an angle or side)
2. (of a bract, stem, etc) to have (a bud or similar part) growing in its axil

Etymology: 16th Century: from Latin subtendere to extend beneath, from sub- + tendere to stretch out