Cold
い adjective
This is a single kanji with an い on the end, meaning you know it's probably an adjective. What's the adjective form of cold? It's cold.
寒い is used specifically for when you feel cold. You can say it when you're outside on a chilly winter day, for example, or when you walk into a cold room. It can even be used as a response to unfunny jokes that leave you cold.
Since this word consists of a kanji with hiragana attached, you can bet that it will use the kun'yomi reading which you learned with the kanji (Samurai (さむ)). Remember?
今日はとても寒いです。
It is very cold today.
この寒い中、一時間もバスを待たなきゃならなかったんだよ。
I had to wait an hour in this cold for the bus.
僕がハワイに行くのは、寒さから逃れるためだけではなく家族に会うためでもあります。
I’m going to Hawaii not only to escape the cold, but to see my family.