He said no but he didn't give a reason.

他说不行，但没有说明原因。

《牛津词典》

Rules are there for a reason.

规则的存在是有原因的。

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He said the election of a citizen to the office of president should not be a reason for dissolving the Union.

VOA: special.2009.07.16

You begin to hear, or perhaps smell, the slight whiff of jargon that pervades theoretical writing. It often does so for a reason.

你开始听出，或者嗅出遍布理论文章中的术语的味道,这往往是有道理的。

耶鲁公开课 - 文学理论导论课程节选

In the Epic of Atrahasis we do in fact read of a reason, and the text there states, "The land became wide and the people became numerous.

在《阿特拉哈西斯》中，我们确实能找到愿意，土地扩大，人口激增。

耶鲁公开课 - 旧约导论课程节选

There is a reason the padlock and pita appeal to us, practically as strongly as oranges.

FORBES: Good Food Needs Good Design. A New Italian Museum Exhibit Shows Why.

If the price dropped down to nothing, Amazon might have a reason to acquire the firm.

FORBES: Should Research in Motion Sell BlackBerry and Call it Quits?

But that isn't a reason to despair that elections have happened in the Middle East.

NPR: Rice Faces Senate Questions on Middle East