(Indo-European linguistics) In Proto-Indo-European linguistics, an ablaut form of a root characterized by the absence of the basic ablauting vowel phonemes */e/ and */o/.

(language education, grammar) A structure used to talk about general truths or facts, containing an "if" clause (with a verb in the present tense) and a main clause (with a verb in the present tense).

plural of zero conditional

(mathematics, of a function) Being equal to the zero function and not merely zero at a particular point in its domain.

Resulting in neither a surplus or deficit because gains and losses cancel out.

plural of zero point

The site of the former World Trade Center towers in New York City destroyed on 11 September 2001.

(epidemiology) The initial patient in the population of an epidemiological investigation.

(of cattle) Kept in enclosures and never let out to graze.

plural of ground zero