ἀλλὰ [154 verses](conj) "But" is alla, which means "instead," "otherwise," "but," "still," "at least," "except," "yet," nevertheless," "rather," "moreover," and "nay." Followed by οὐ, the sense is "still," and "at least." Followed by γὰρ. the sense is "but really" and "certainly."  Following an εἰ μὴ, clause the sense is "if not" some word , related to time, "at least still," and without the reference time, "at least"   -- (CW) The Greek word translated as "but" denotes an exception or simple opposition. It is used to emphasize the contrast between things like we use "instead," "but instead,"or "rather." It is not the common word usually translated as "but." It is the Greek word "other" like we use "otherwise." Jesus almost always uses this conjunction to connect a negative clause, "not this," with a positive one, "instead this." CW - Confusing Word -- The "but" is not the common word usually translated as "but" and works differently.