To Let Something Pass
To Put Something Through
transitive 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. You already learned that 通る means to pass, but this is a little different. You aren't the one passing, Sue (す) is. So you have to let Sue pass. In other words, this verb is transitive, meaning it has an object. That's why it means to let something pass or to put something through.
The way this verb is translated into English changes a lot depending on the noun it's paired with. For example 火を通す is literally "to let the fire pass through", and means "to heat through". 針に糸を通す is literally "to put thread through a needle", so means "to thread a needle".
Since this word consists of a kanji with hiragana attached, you can bet that it will use the kun'yomi reading. You learned this reading when you learned 通る. Switch the る for a す and you'll be all set!
ガラスは光を通します。
Glass lets light pass through it.
お肉には、しっかり火を通してください。
Please heat the meat thoroughly.
会ったばかりの他人を家に通しちゃダメです。
Never let others who you just met into your home.