(poetic) Contraction of his.

(UK, dialect) Contraction of as (when it is (nonstandardly) used as a relative conjunction, or like a relative pronoun, meaning "that").

(UK, dialect) Contraction of as.

(physics) subatomic particles with a spin (quantum angular momentum) of 0, predicted by supersymmetry; the bosonic equivalent of known fermions

(organic chemistry) secondary form

The nineteenth letter of the English alphabet, called ess and written in the Latin script.

The ordinal number nineteenth, derived from this letter of the English alphabet, called ess and written in the Latin script.

Initialism of south. / Initialism of season (group of episodes of a series). / (usually clothing, singular only) Initialism of small (the manufactured size or an item of that size).

(usually clothing) Initialism of small (of the manufactured size).

(set theory) An axiomatic set theory, developed by logician George Boolos, in which several of the axioms of ZF are derivable as theorems.