noun
A letter or notice sent to multiple recipients in turn, often for official or organizational communication.
町内会の回章が回ってきた。
The neighborhood association's circular came around.
noun
response letter; reply letter
A letter written in reply; often used in formal or written correspondence. Cross-referenced with 返書.
See also: 返書
先日のお手紙に対する回章をしたためました。
I wrote a reply to your recent letter.
返書 is a more common term for a reply letter; 回章 (sense 2) is a less frequent synonym.
Compound of 回 (circulate) and 章 (document/writing). The exact historical derivation is uncertain.