Surdus

Surdu s is a Latin adjective meaning deaf, unable to hear. In classical Latin it described people or animals with hearing loss and could extend metaphorically to silence or inaudibility. The feminine form is surda and the neuter surdum, with surditas denoting deafness as a noun. The term appears in various Latin texts to indicate lack of hearing or sound, and it contributes to related vocabulary in later languages.

In English, surd (singular) and surds (plural) is a mathematical term for an irrational number or a radical expression that cannot be simplified to remove the radical sign. Examples include the square root of 2 or the cube root of 3. Surds are manipulated according to standard algebraic rules: they can be factored, added or subtracted when they are like surds, and denominators containing surds may be rationalized. The concept is foundational in algebra, pre-calculus, and number theory and is distinguished from rational numbers, while also contrasting with transcendental numbers in broader mathematical contexts.

Etymology and usage notes: surdus is the Latin origin of the word, and the mathematical term surd in English derives from this root through historical usage. The two senses—linguistic (deaf) and mathematical (irrational or non-simplifiable radical)—occupy different domains but share the same ancestral root in Latin.