noun
Refers to one's mental state, mood, or emotional disposition. Often used in expressions like 心気を養う (nurture one's mind) or 心気が沈む (feel depressed).
最近、心気が沈みがちだ。
Lately, I tend to feel down.
読書は心気を養うのに良い。
Reading is good for nurturing one's mind.
noun, na-adjective
fretfulness; irritation; tedium
Describes a state of being fretful, irritated, or feeling that something is tedious. Often used in the phrase 辛気臭い (しんきくさい) meaning 'irritatingly tedious' or 'fretful'. The kanji 辛気 is especially associated with this sense.
彼の愚痴を聞くのは辛気臭い。
Listening to his complaints is irritatingly tedious.
待ち時間が長くて、辛気が募った。
The long wait made me increasingly fretful.
心気 combines 心 (heart/mind) and 気 (spirit/energy), referring to one's mental state. 辛気 uses 辛 (bitter/painful) to emphasize the fretful, irritating aspect. The exact historical derivation is uncertain, but the spellings are conventionally associated with these meanings.