じゃないです

• “[Noun] + じゃないです” is the negative counterpart to “[Noun] です” (desu), which means “is [noun]”
• じゃない (ja nai) is the negative form
• です (desu) is added at the end to make it polite

Additional Notes:

• This is a slightly more casual form. The more formal version would be “[Noun] ではありません” (dewa arimasen). Note that では (dewa) is just the formal version of じゃ (ja); じゃ is a contraction of では.
• In very casual speech, people might drop the です and just say “[Noun] じゃない”
• The question form would be “[Noun] じゃないですか”

Important Notes

• Textbook Rule: A noun should always precede じゃないです/ではありません.This is grammatically complete and perfectly correct, especially for learners:
  • Q: 日本人ですか？
  • Textbook response: いいえ、日本人じゃないです。
• Real-Life Spoken Japanese: In real conversations, Japanese speakers often omit the noun when it’s obvious from context:
  Q: 日本人ですか？
  A: いいえ、じゃないです。
  It’s natural, efficient, and very common — just like how we often drop repeated info in English:
  Q: Are you Japanese?
  A: No, I’m not. (We don’t say “No, I’m not Japanese.” every time.)