「安全」 (あんぜん) means "safety" as a noun or "safe" as a な-adjective. It refers to being free from danger or risk. You use it when talking about protecting people or things from harm. This park is safe for children.

「安全」は、危険がなく、安心できる状態を意味します。この公園は子供たちにとって安全です。