a mirror; a glass or metal surface that reflects an image.
朝起きて鏡で顔を確認する。
I check my face in the mirror after waking up.
鏡に映った自分の姿を見て驚いた。
I was surprised by my reflection in the mirror.
鏡を壁に掛ける。
Hang a mirror on the wall.
barrel head; a lid or board forming part of a barrel or similar object (technical term).
樽職人は古い鏡を交換して樽を修理した。
The cooper repaired the barrel by replacing the old barrel head.
a front page added to a document listing its purpose, date, author, etc. (finance/accounting usage).
提出書類には鏡を付けて作成日と目的を明記した。
I attached a 'kagami' to the submitted documents and specified the date and purpose.
abbreviation of kagami-mochi — the round rice cake displayed at New Year.
正月に実家で小さな鏡を飾った（鏡＝鏡餅）。
At New Year I decorated my parents' house with a small kagami (kagami = kagami-mochi).