a suffix appearing in loanwords from Greek, where it was used to form from verbs abstract nouns of action, process, state, condition, etc.: thesis; aphesis.
n. sister. (Also a term of address and a common pet name for one's sister.) : Come on, sis. We're going to be late.
Dictionary of American Slang and Colloquial Expressions by Richard A. Spears.Fourth Edition. Copyright 2007. Published by McGraw Hill.
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Word Origin & History
sis
1656, abbreviated form of sister; in Amer.Eng., applied generally to girls and young women (1859).
-sis
suffix in Gk. nouns denoting action, process, state, condition, from Gk. -sis, which is identical in meaning with L. -entia, Eng. -ing.