(of a number) irrational.
(of a speech sound) uttered with the breath and not the voice (e.g. f, k, p, s, t).
A surd number, especially the irrational root of an integer.‘They were learning about surds in maths, supposedly one of the hardest subjects.’
- ‘I don't care about rationalising denominators with surds in them, and I don't care that by using maths induction you can prove many equations to be right or wrong.’
- ‘In the conventional school education in India, we are asked to do some problems involving surds (radicals).’
A surd consonant.
Mid 16th century from Latin surdus ‘deaf, mute’; as a mathematical term, translating Greek (Euclid) alogos ‘irrational, speechless’, apparently via Arabic jiḏr aṣamm, literally ‘deaf root’. surd (sense 2 of the adjective) dates from the mid 18th century.