How to say "gladly" in Japanese

• 喜んでよろこんでCommon
  adverbThe default choice for 'gladly' in the sense of agreeing to a request with pleasure, as in accepting an invitation or offer politely and willingly. This is the common word learners will usually want.
  喜よろこんでご招待しょうたいに応おうじます。↗

  I will be very happy to accept your invitation.
• 得たり賢しえたりかしこし
  expression, adverb (with と)A dated idiom covering only 'gladly' in the sense of taking advantage of something, pouncing on an opportunity. For ordinary 'gladly' it is not the word you want; it belongs to that specific 'readily seizing a chance' meaning.
• 快くこころよく
  adverbCovers 'gladly' as doing something willingly and readily, with the nuance of accepting or complying with good grace, without reluctance. Less common than 喜んで, and suits contexts of agreeing to a request or helping out.

Use 「喜んで」 for the ordinary polite 'gladly, with pleasure'; 「快く」 for willingly and readily doing something; 「得たり賢し」 is a dated idiom only for gladly seizing an opportunity.

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

• 喜んでよろこんでwith pleasure
• 得たり賢しえたりかしこしhappily (e.g. seizing an opportunity)
• 快くこころよくwillingly