SI Meaning of SI in English adv 1. thus, so; 2. yes; si ... como as ... as, (not) so ... as conj if (1. supposing that; 2. whether); si non 1. if not; 2. except, unless it be n 1. [Mus.] ti, si; 2. [Mus.] (the note) B Interlingua English vocab. Английский словарь Интерлингва. 2012