To Stop
intransitive verb, godan verb
This word consists of kanji with hiragana attached. Because the hiragana ends with an う sound, you know this word is a verb.
This is an intransitive verb. That means it does not take a direct object. Something comes to a stop. No direct object here. That's why this verb means to stop.
とまる
Since this word consists of a kanji with hiragana attached, you can bet that it will use the kun'yomi reading. You didn't learn that reading with this kanji, so here's a mnemonic to help you:
You come to a stop sign and decide to stop because the sign has a picture of a toe (と) on it. This toe looks eerily like a toe your Ma (ま) has too... and your Ma always taught you to stop and look both ways before crossing her toes.
あかしんごうで、くるまは止まりました。
The car stopped at the red signal.
心ぞうが止まるかとおもった。
I was so surprised I thought my heart leapt into my mouth.
こおりの上で、止まることができなかった。
I couldn’t stop on the ice.