必ずしも

Negative of 必ず (kanarazu, “without fail”)

必(かなら)ずしも • (kanarazushimo) 

1. not always, not all
   • c. 800, Han Yu, On Teaching(師說):

     是(こ)の故(ゆえ)に弟(てい)子(し)は必(かなら)ずしも師(し)に如(し)かずんばあらず、師(し)は必(かなら)ずしも弟(てい)子(し)より賢(けん)ならず。

     Kono yue ni teishi wa kanarazushimo shi ni shikazunba arazu, shi wa kanarazushimo teishi yori ken narazu.

     For this reason, apprentices do not have to be inferior to their masters; masters do not have to be more virtuous than their apprentices.

• Used with negative forms of verbs as a double negative, which is grammatically correct in Japanese.
• Sometimes paired with とは限らない in written Japanese.