How to say "additionally" in Japanese

• 付け加えるとつけくわえると
  adverbUsed for 'additionally' when you are appending a supplementary remark — adding one more point after what has already been said. It frames the new statement as something tacked on to the rest.
• 加えてくわえて
  conjunctionAdds another item, reason or point on top of what has been said, close to 'moreover'; it can also present the added element as coming alongside the rest ('at the same time').
• 事前後じぜんご
  noun, adverbGlossed 'subsequently; additionally', but its core sense is 'subsequently' — something happening after the event. For plain 'in addition' it is a marginal choice, and being less common, it is seldom the word learners want.
• 別にべつにJLPT N3approx.Common
  adverbA common word, but its 'additionally' is the 'extra' sense: an added amount or item kept separate from the main one, not a 'moreover'-style connector between statements.
  ソースを別べつにください。↗

  I'd like the sauce on the side.

For adding a further remark or item use 「付け加えると」 or 「加えて」 (the latter close to 'moreover'); use 「別に」 only for an extra, separate item; 事前後 mainly means 'subsequently' and is seldom the right choice.

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

• 付け加えるとつけくわえるとadditionally
• 加えてくわえてadditionally
• 事前後じぜんごsubsequently
• 別にべつにseparately