subtend

[ suh b-tend, suhb- ]

/ səbˈtɛnd, sʌb- /

Geometry. to extend under or be opposite to: a chord subtending an arc.

Botany. (of a leaf, bract, etc.) to occur beneath or close to.

to form or mark the outline or boundary of.

Origin of subtend

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

Unless they subtend a high vertical angle to the vision they produce little effect.

The Alps |Martin Conway
In like manner the two pale are bracteoles which subtend the flower proper.

Grasses |H. Marshall Ward
Undersea, submarine; underspan, subtend; underslinking, subterfuge.

An Outline of English Speech-craft |William Barnes
For this purpose the condenser should subtend as large an angle as possible at the source of light.

Encyclopaedia Britannica, 11th Edition, Volume 16, Slice 2 |Various

"Subtend" is from the Latin sub (under), and tendere (to stretch).

The Teaching of Geometry |David Eugene Smith

subtend

/ (səbˈtɛnd) /

geometry to be opposite to and delimit (an angle or side)

(of a bract, stem, etc) to have (a bud or similar part) growing in its axil

to mark off

to underlie; be inherent in

C16: from Latin subtendere to extend beneath, from sub- + tendere to stretch out