返書|へんしょhensho[1]atamadaka (head-high)

1. nounreply (to a letter); response; answer

• Synonym返事へんじNeutralThe most general word for a reply, in speech or writing; unlike 「返書」, it is not limited to letters and is neither formal nor old-fashioned.
• Synonym返信へんしんNeutralThe usual word for a reply to a letter or email, as in 「返信用封筒」; much more modern and common than 「返書」.
• Synonym返答へんとうNeutralAn answer to a question or call, in speech or writing, as in 「返答に困る」; 「返書」 refers only to a reply letter.
• SynonymリプライNeutralColloquial loanword for a reply, used mostly on social media; 「返書」 is a formal, old-fashioned letter term.
• Related答えこたえNeutralThe most general word for an answer or solution; unlike 「返書」, it is not specific to letters.
• Related回答かいとうNeutralWritten word for a formal answer to a question, as in 「アンケートの回答」; it answers inquiries rather than naming a reply letter.
• Related応答おうとうWrittenWritten word for answering a question or call, also a reaction to stimuli, as in 「応答なし」; 「返書」 means only a reply letter.
• Related受け答えうけこたえNeutralHow one responds in question-and-answer exchanges, as in 「受け答えがしっかり」; not a term for letters.
• RelatedレスNeutralInternet slang for a reply to a post on a bulletin board or social media; colloquial, unlike the formal 「返書」.
• RelatedアンサーNeutralColloquial loanword for an answer or solution; unlike 「返書」, it does not refer to letters.
• RelatedレスポンスNeutralLoanword for a reaction or response, often of speed, as a computer's 「レスポンス」; not a word for reply letters.
• Related返り言かえりごとWrittenArchaic term for a message a messenger brings back home, also a reply poem or return gift; carries a classical flavor.
• Related復答ふくとうWrittenWritten word for a reply, but rarely used; 「返答」 is the usual choice.
• Antonym来書らいしょWrittenA written term for a letter received from the other party; the counterpart of the reply letter 「返書」.

「返書」 is a written, old-fashioned word for a reply letter. Everyday replies are 「返事」, replies to letters or emails 「返信」, answers to questions 「返答」. 「回答」 fits formal answers like surveys, 「応答」 responses to calls or stimuli, 「リプライ」 and 「レス」 online replies, 「答え」 and 「アンサー」 general answers, 「レスポンス」 reactions. 「来書」 is the letter received.

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

1. 返事へんじの書簡しょかん。返信へんしん。