surd

Meanings

Noun

• An irrational number, especially one expressed using the √ symbol.
• A voiceless consonant.

Adjective

• Lacking the sense of hearing; deaf.
• unheard
• Involving surds, or irrational numbers; not capable of being expressed in rational numbers.
• unvoiced; voiceless

Origin

• Borrowed from Latin surdus ("deaf"); in mathematical sense, "deaf to reason", i.e. irrational.