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From Latin subtendere, from sub (under) + tendere (to stretch, extend). See tend.


  • IPA(key): /sʌbˈtɛnd/
  • (file)
  • 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.