n.
Pronunciation: ' b ə t
Function: conjunction
Etymology: Middle English, from Old English b ū tan, preposition & conjunction, outside, without, except, except that; akin to Old High German b ū zan without, except; akin to Old English be by, ū t out ― more at BY , OUT
Date: before 12th century
1 a : except for the fact <would have protested but that he was afraid> b : THAT ― used after a negative <there is no doubt but he won> c : without the concomitant that <it never rains but it pours> d : if not : UNLESS e : THAN <no sooner started but it stopped> ― not often in formal use
2 a : on the contrary : on the other hand : NOTWITHSTANDING ― used to connect coordinate elements <he was called but he did not answer> <not peace but a sword> b : YET <poor but proud> c : with the exception of ― used before a word often taken to be the subject of a clause <none but the brave deserves the fair ― John Dryden>
– but that : THAT ― used after a negative <there is no doubt but that it must be done>
– but what : that ⋯ not ― used to indicate possibility or uncertainty <I don't know but what I will go>