1.
key point, gist, crux
The most important or essential part of something. The critical element that determines success or failure.
そこが肝だ。
That's the key point.
タイミングが肝だ。
Timing is crucial.
この料理の肝は、火の通し方にある。
The key to this dish lies in how you control the heat.
2.
liver; innards, guts
The liver organ, or more broadly the internal organs. Also used figuratively to refer to courage or nerve.
肝が据わっている。
To have guts; to be bold.
肝を冷やした。
It gave me a fright.
彼は肝が太いから、どんな場面でも動じない。
He has nerves of steel, so he stays calm in any situation.
USAGE:
Sense 1 is common in everyday conversation to identify the most important aspect of something. 〜が肝だ means "~ is the key."
Sense 2 appears mainly in set expressions involving courage, fear, or surprise.
COMMON EXPRESSIONS:
- 肝が据わる: to have guts, to be unflinching
- 肝を冷やす: to be frightened, to have a scare
- 肝が太い: bold, nervy
- 肝試し: test of courage (haunted house, etc.)
COMMON COLLOCATIONS:
- 肝心な点: crucial point (compound using 肝)
- 〜が肝: ~ is the key