The doctor advised him to use his inhaler before exercise to prevent asthma attacks.

inhaler 是由动词 inhale（吸入）加上名词后缀 -er 构成的名词，指"吸入装置"。in- 表示"进入"，-hale 来自拉丁语 halare（呼吸），所以 inhaler 字面意思是"帮助呼吸进入体内的器具"，即"吸入器"。