～とは限らない— Not Necessarily So

• 高いものがいいとは限らない。

  Takai mono ga ii to wa kagiranai.

  Expensive things are not necessarily good.

  いい (good, plain) + とは限らない denies the assumption that price equals quality

• 日本人だからといって、寿司が好きだとは限らない。

  Nihonjin da kara to itte, sushi ga suki da to wa kagiranai.

  Just because someone is Japanese doesn't mean they necessarily like sushi.

  な-adj 好きだ + とは限らない rejects the stereotype

• 努力すれば必ず成功するとは限らない。

  Doryoku sureba kanarazu seikou suru to wa kagiranai.

  Making an effort doesn't necessarily mean you will succeed.

  Verb 成功する + とは限らない; often paired with 必ず (always) to stress the exception

• ・Often appears with adverbs like 必ずしも or いつも to reinforce the 'not always' meaning.
• ・Register: neutral; common in essays and discussion.
• ・It denies a general rule, not a specific single fact.

Commonly confused with

The JLPT rarely asks whether you recognise a pattern — it asks which of several similar patterns fits. These are the ones ～とは限らない is tested against.

• ～おそれがある — There Is a Risk That
• ～ことだ — You Really Should
• ～ことはない — No Need To
• ざるを得ない — No Choice But To
• っこない — No Way That'll Happen
• ～てみせる — I'll Show You I Can
• ～に決まっている — I'm Sure It Must Be
• ～ほかない／～ほかはない — No Choice But To