Surd (?), a. [L. surdus deaf (whence the meaning, deaf to reason, irrational), perhaps akin to E. swart. Cf. Sordine.]


Not having the sense of hearing; deaf.

[Obs.] "A surd . . . generation."

Sir T. Browne.





3. Math.

Involving surds; not capable of being expressed in rational numbers; radical; irrational; as, a surd expression or quantity; a surd number.

4. Phonetics

Uttered, as an element of speech, without tone, or proper vocal sound; voiceless; unintonated; nonvocal; atonic; whispered; aspirated; sharp; hard, as f, p, s, etc.; -- opposed to sonant. See Guide to Pronunciation, §§169, 179, 180.


© Webster 1913.

Surd, n. Math.


A quantity which can not be expressed by rational numbers; thus, √2 is a surd.

2. Phon.

A surd element of speech. See Surd, a., 4.


© Webster 1913.