必ずしも

1. Origins, structure, and basic meaning

• Structure: 必ずしも is read かならずしも.
• Basic usage: It means “not necessarily” and is used with negative expressions such as ～ない, とは限らない, or わけではない to reject an absolute generalization.

2. Common pitfalls and similar expressions

• With とは限らない
  • 必ずしも長持ちするとは限らない means that being expensive does not guarantee that something will last.
• With わけではない
  • 必ずしも正解につながるわけではない means that answering quickly does not always lead to the correct answer.