Definition of subtend
1a : to be opposite to and extend from one side to the other of <a hypotenuse subtends a right angle>b : to fix the angular extent of with respect to a fixed point or object taken as the vertex <a central angle subtended by an arc> <the angle subtended at the eye by an object of given width and a fixed distance away>c : to determine the measure of by marking off the endpoints of <a chord subtends an arc>
2a : to underlie so as to includeb : to occupy an adjacent and usually lower position to and often so as to embrace or enclose <a bract that subtends a flower>
Origin and Etymology of subtend
Latin subtendere to stretch beneath, from sub- + tendere to stretch — more at thin
First Known Use: 1570
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