1) Be opposite to 2) Delimit 
to stand beneath or close to, as in a bract at the base of a flower.
being immediately below something
to be opposite to or to extend under
• (v. t.) To extend under, or be opposed to; as, the line of a triangle which subtends the right angle; the chord subtends an arc.
To support another structure or organ.
to occupy a position below and adjacent to
to occupy a position below and adjacent to
Attached below and extending upward.
To extend under; found at the base of.
Sub·tend' transitive verb [ imperfect & past participle Subtended ; present participle & verbal noun Subtending .] [ Latin subtendere ; sub under + tendere to stretch, extend. See Tend .] To extend under, or...
being immediately below something
[v] - be opposite to
subtend To extend under or be opposite to in position [to stretch underneath].
Subtend (of a bract) extend under (a flower) so as to support or enfold it.
Subtend (of a bract) extend under (a flower) so as to support or enfold it.
to extend under or be opposite to: a chord subtending an arc. · (of a leaf, bract, etc.) to occur beneath or close to. · to form or mark the outline or boundary of.