preheated 是形容词,由动词 preheat 的过去分词转化而来,具有被动和完成含义。它通常作定语修饰名词,如 preheated oven、preheated air,也可作表语,如 The oven is preheated. 及物动词 preheat 常用于被动结构:The oven should be preheated to 180°C. 易错点:preheated 本身已含「被加热」之意,无需再加被动助动词,如不说 be preheated by someone;作定语时通常前置,但也可后置以强调,如 the oven preheated to 200°C。注意与现在分词 preheating 区分,后者表示主动或进行。