Used in the phrase 月の欠け (the waning moon) or in astronomical contexts. Not a common standalone word for the moon's phase in everyday conversation.
Observe the waning of the moon.
I cut my finger on a splinter of wood.
欠ける is the intransitive verb meaning 'to be chipped' or 'to be missing a piece'; 欠け is the noun form derived from it.
chip; break off; be damaged · be missing; be absent; become lost · be lacking; be short of; be deficient · wane (moon); go into eclipse
waxing and waning (of the moon)
chip; missing piece; broken part · short weight; underweight · false eye
self-exile; going into hiding
pixel defect; dead pixel
pixel defect; dead pixel
Standard kanji spelling for both senses.
Kana spelling is common in everyday writing, especially when the kanji is not needed for clarity.
Rarely used kanji form.
Contains outdated kanji; not used in modern Japanese.
Noun form of the verb 欠ける (to be chipped, to be missing). The kanji 欠 is associated with 'lack' or 'gap'.