How to say "avail" in Japanese

• 甲斐かいCommon
  nounRead かい, this is the common word for 'avail' as a noun: the worth or effect that makes an effort worthwhile, as when you say an effort paid off or was to no avail.
  苦心くしんの甲斐かいがあった。↗

  That was well worth the trouble.
• 甲斐がい
  suffixThe same word with the less common voiced reading がい. For the 'avail' sense you will normally want かい; がい you will meet chiefly inside compounds rather than standing alone.

Both entries are a single word, 甲斐, meaning the worth or effect that makes an effort worthwhile ('avail'); choose the common reading かい, while がい is its less common voiced form, heard chiefly within compounds.

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

• 甲斐かいresult (that makes an act worthwhile)
• 甲斐がいresult (that makes an act worthwhile)