To Change Something
To Revise Something, To Correct Something
transitive verb, ichidan verb
This word consists of kanji with hiragana attached. Because the hiragana ends with an う sound, you know this word is a verb.
The kanji itself means renew, and this verb's meaning isn't far off. What do you do if you renew something, usually to make it better? You're going to change something, to revise something, or to correct something. This verb is transitive, so it takes a direct object.
改める is a formal word for when you're actively make changes or improvements, like fixing a mistake or reforming a system. You might also use it when you decide to change your behavior or update your way of doing something.
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:
Usually when we want to change something, we want to make it 新た (あらた), right? Out with the old, in with the 新た, as they say.
日を改めることにしました。
We decided to change the date.
その考え方は改めた方がいいよ。
You should correct that way of thinking.
話し合った通りに計画を一部改めた。
Just as we discussed, we revised a part of the plan.