You can use continual, continuous, and constant to describe things that happen or exist without stopping. Continual is usually used to describe something that happens often over a period of time, especially something undesirable. ...his continual drinking. ...continual demands to cut costs. If something is continuous, it happens all the time without stopping, or seems to do so. ...days of continuous rain. ...a continuous background noise. You describe something as constant when it happens all the time or never goes away. He was in constant pain. ...Eva's constant criticism.

continual, continuous 和 constant 都可以用来描述不间断地发生或一直存在的事物。continual 表示一段时期内经常发生，尤其是令人不快的事情：his continual drinking (他持续饮酒)，continual demands to cut costs (对于削减成本的再三要求)。continuous 则表示一刻不停，或看似如此：days of continuous rain (淫雨霏霏的日子)，a continuous background noise (一刻不停的背景噪声)。constant 表示一直在发生，或从不消失:He was in constant pain (他的疼痛一直没有消停)，Eva's constant criticism (伊娃不断的批评)。