Mouth
noun
When a vocab is made up of a single kanji with no okurigana (hiragana attached to the kanji) it's generally going to have the same meaning as the kanji it came from. From that, you know this word's meaning is mouth.
When a vocab is a single kanji and all alone like this, it's usually going to use the kun'yomi, which you did not learn from learning the kanji. To remember this word, you should use a mnemonic. With your mouth, make a "kuchi kuchi kou" (くち) sound. Go ahead, make it. Focus on your mouth and try to imagine each shape it makes while zooming in on it. You're talking to a baby, which is why you're making all these ridiculous noises. Also, instead of "coo" at the end, you're saying "kou," because that's the reading of the kanji (こう).
くちくちこう！くちくちこう！ Sounds like something from Arrested Development, actually.
口にくわえる
to put something in one's mouth
口に入る
to enter one's mouth, to get something in one's mouth
口にする
to mention, to eat, to drink
口をそろえる
to protest in chorus, to speak in unison
口をあける
to open one's mouth
口をひらく
to open one's mouth to speak
ワニの口
crocodile's mouth
バッグの口
the opening of a bag
ペットボトルの口
the mouth of a plastic bottle
口のまわり
around one's mouth
口のケア
oral care
口のトラブル
oral problems
口にソースがついていますよ。
There is some sauce on your mouth.
これを口に入れてください。
Please put this in your mouth.
このペットボトルは口が大きすぎる。
The mouth of this plastic bottle is too large.
ちゃんと口のケアをしないと、女にモテないだろ。
If you don't take good care of your mouth, you won't have much luck with women.