jukujikun; special kanji compound reading
A reading assigned to a kanji compound where the characters relate to the meaning but not the pronunciation; e.g. 昨日 (きのう), 大人 (おとな). Used in Japanese linguistics.
Jukujikun is a reading where a native Japanese word is matched to the meaning of the kanji compound.
「明日」を「あした」と読むのも熟字訓の一つだ。
Reading 明日 as あした is also an example of jukujikun.
当て字 uses kanji chosen for sound or meaning without regard to standard readings, while 熟字訓 is a kanji compound that as a whole is given a native Japanese reading unrelated to the individual characters' sounds (e.g. 大人 read おとな).
From 熟字 (jukuji, 'kanji compound') + 訓 (kun, 'native Japanese reading'). The term describes a reading where the whole compound is read with a native Japanese word that matches its meaning, rather than by combining the individual character readings.