·noun Six. ·see Sise.
II. Sis ·noun A colloquial abbreviation of Sister.
sīs . I Subj. of sum.— II Contr. from si vis; v. volo init. — III I. q. suis, v. suus init. ...
A New Latin Dictionary by Charlton T. Lewis Ph.D. and Charles Short, LL. D.
sīs (1) subj.of sum. ...
An Elementary Latin Dictionary