sesqui-

CIDE DICTIONARY

sesqui-,  [L., one half more, one and a half.].

 A combining form (also used adjectively) denoting that three atoms or equivalents of the substance to the name of which it is prefixed are combined with two of some other element or radical; as, sesquibromide, sesquicarbonate, sesquichloride, sesquioxide.  [1913 Webster]
" Sesquidupli- is sometimes, but rarely, used in the same manner to denote the proportions of two and a half to one, or rather of five to two."  [1913 Webster]

OXFORD DICTIONARY

sesqui-, comb. form 1 denoting one and a half.
2 Chem. (of a compound) in which there are three equivalents of a named element or radical to two others.

Etymology

L (as SEMI-, -que and)

ROGET THESAURUS

sesqui-

Unity

N unity, oneness, individuality, solitude, isolation, unification, one, unit, ace, individual, none else, no other, one, sole, single, solitary, unitary, individual, apart, alone, kithless, unaccompanied, unattended, solus, single-handed, singular, odd, unique, unrepeated, azygous, first and last, isolated, insular, monospermous, unific, uniflorous, unifoliate, unigenital, uniliteral, unijocular, unimodal, unimodular, lone, lonely, lonesome, desolate, dreary, insecable, inseverable, indiscerptible, compact, indivisible, atomic, irresolvable, singly, alone, by itself, per se, only, apart, in the singular number, in the abstract, one by one, one at a time, simply, one and a half, sesqui-, natura il fece, e poi roppe la stampa, du fort au faible, two souls with but a single thought, two hearts that beat as one.