subtend

From Latin subtendere, from sub (“under”) + tendere (“to stretch, extend”), itself a semantic loan from Ancient Greek ὑποτείνω (hupoteínō, “to subtend”), from which hypotenuse also derives. See tend.

• IPA^(key): /sʌbˈtɛnd/

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• Rhymes: -ɛnd

subtend (third-person singular simple present subtends, present participle subtending, simple past and past participle subtended)

1. (transitive, mathematics) To use an angle to delimit (mark off, enclose) part of a straight or curved line, for example an arc or the opposite side of a triangle.

   A 43° angle subtends an arc of about 0.75 meters on a circle with a radius of 1 meter.

2. (transitive, also mathematics) To extend or stretch opposite something; to be part of a straight or curved line that is opposite to and delimits an angle.

   A hypotenuse subtends the right angle of a right triangle.

   An arc measuring about 0.75 meters on a circle with a radius of 1 meter subtends an angle of about 43°.

   • 2012 August 16, “Me, myself, us”, in The Economist, issue:

     […] trillions of bacteria, each equally an individual, which are found in a person’s gut, his mouth, his scalp, his skin and all of the crevices and orifices that subtend from his body’s surface.

3. (transitive, mathematics) To form the central angle of a circle underneath an arc.

   The points A and B on the circumference form the arc AB, which subtends the central angle θ.

4. (botany, transitive) To stand beneath or close to, as a bract at the base of a flower.

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