1
[ADJ 形容词]持续不断的；重复的；一直存在的 You use
constant to describe something that happens all the time or is always there.
She suggests that women are under constant pressure to be abnormally thin...
她暗示说女性总是处在保持身材异常瘦削的压力之下。
Inflation is a constant threat...
通货膨胀始终是个威胁。
He has been her constant companion for the last four months.
4个月来，他一直陪伴在她身边。
2
[ADJ-GRADED 能被表示程度的副词或介词词组修饰的形容词]恒定的；不变的 If an amount or level is
constant, it stays the same over a particular period of time.
3
[N-COUNT 可数名词]恒定物；常数；常量；常项 A
constant is a thing or value that always stays the same.
In the world of fashion it sometimes seems that the only constant is ceaseless change...
在时装界，有时似乎唯一永恒不变的东西就是不断的变化。
Two significant constants have been found in a number of research studies.
若干研究已经发现了两个重要常量。
Usage Note :
You can use constant, continual, and continuous to describe things that happen or exist without stopping. 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 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.
constant, continual 和 continuous 均可用来描述不断发生或一直存在的事物。constant 表示一直在发生或从未消失：He was in constant pain (他的疼痛一直没有消停)，Eva's constant criticism (伊娃没完没了的批评)。continual 通常用来形容一段时期内经常发生的事，尤其是令人讨厌的事：his continual drinking (他经常饮酒)，continual demands to cut costs (不断要求削减成本)。continuous 表示一直没有间断，或者貌似如此：days of continuous rain (淫雨霏霏的日子)，a continuous background noise (持续不断的背景噪音)。