1、vital

必要的;至关重要的;必不可少的

The port is vital to supply relief to millions of drought victims.

这个港口对向数百万旱灾灾民提供救援物资是至关重要的。

Nick Wileman is a school caretaker so it is vital that he gets on well with young people.

尼克·威尔曼是学校的管理员，因此与年轻人搞好关系很重要。

充满活力的;生气勃勃的

They are both very vital people and a good match.

他俩都很有活力，十分般配。

They have something important to say and vital and radical ways of saying it.

他们有些重要的事情要说，言辞会比较激烈。

2、constant

持续不断的;重复的;一直存在的

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。

恒定物;常数；常量；常项

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。

恒定的;不变的

The average speed of the winds remained constant.

平均风速保持稳定。