I reached that certain age and fell in love.

我到了既定年龄却陷入爱河。

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Human brains come equipped with certain quantitative instincts that are refined with age, but these instincts are very limited.

随着年龄的增长，人类的大脑具有了一定的数量本能，但这种本能是非常有限的。

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Certain features of these engravings lead to the conclusion that they are of great age—geological changes had clearly happened after the designs had been made.

这些雕刻的某些特征让人得出它们年代久远的结论——这些设计完成之后显然有地质变化发生。

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But almost one in five (19%) said that being middle age is a state of mind, rather than something that begins at a certain age.

BBC: Middle age begins at 55 years, survey suggests

Second step: They can sign a contract--symbolic, not binding--stipulating that, by a certain age (provided the business is not in financial distress) that they will move on and let the next generation take its lumps.

FORBES: Head Coach

Newt Gingrich reminds me of one of those small, ugly dogs that women of a certain age make a tremendous fuss over.

BBC: Newt Gingrich and his campaign legacy