How to say "invaluable" in Japanese

• 値千金あたいせんきん
  no-adjectiveCovers 'invaluable' in the sense of immense worth: literally 'worth a thousand gold pieces,' it describes something so valuable as to be beyond price, such as a precious experience or timely help.
• 二つとないふたつとない
  expression, i-adjectiveCovers 'invaluable' through uniqueness: literally 'there is no second one,' it presents something as one of a kind and therefore irreplaceable, its value lying in there being no other like it.

Choose 値千金 when you mean worth beyond money, like a fortune, and 「二つとない」 when the point is uniqueness and irreplaceability; both are less common ways to render 'invaluable' in Japanese.

Usage comparisons are AI-assisted and cross-checked by multiple models; for study reference only

• 値千金あたいせんきんpriceless
• 二つとないふたつとないunique