noun which may take the genitive case particle 'no', noun
oral; inside the mouth
Used in medical, dental, or formal contexts to refer to the interior of the mouth. Often appears in compounds like 口内炎 (mouth ulcer) or 口内検査 (oral examination).
口内炎ができて、食事がつらい。
I have a mouth ulcer and eating is painful.
Maybe because of the fever, my mouth is extremely dry.
歯科医が口内を詳しく調べた。
The dentist examined the inside of my mouth in detail.
To prevent cavities, it's important to keep the inside of your mouth clean.
After eating something hard, I got a small cut inside my mouth.
口内 (the inside of the mouth) and 校内 (within the school grounds) are pronounced identically but refer to completely different things.
口内 (inside the mouth) and 構内 (the premises or grounds of a facility, e.g. 駅構内) share the same pronunciation but have unrelated meanings.
mixing rice and side dishes in one's mouth
mouth ulcer; stomatitis
oral sex; fellatio
Standard kanji spelling for 'inside the mouth' or 'oral'.
Irregular kanji usage; 咥 is not standard for this meaning. Rarely encountered.
Compound of 口 (mouth) and 内 (inside). The reading こうない is the on'yomi of both characters.