A question from a former nursing student made our blood run cold and our heart constrict. Why, she wanted to know, does our lexicon contain the words dilation and dilatation? How did we come up with two words—one with a seemingly extra syllable—with the same meaning? (来源：EnglishCN.com)

We're exaggerating about our bodily response—and we point out that we have absolutely no medical training—but we can appreciate a sometime distinction between dilation and dilatation.

The two terms share an ancestor in the Latin dilatare, literally, "to spread wide." Dilatation, the longer word, is also older. Back in the 14th century, it had two meanings: "amplification in writing or speech, especially by the addition of discussion, illustration, or detail" and "the condition of being stretched beyond normal dimensions, especially as a result of overwork or disease or of abnormal relaxation."

In addition to those meanings, dilatation also has a sense synonymous with dilation. Dilation (which dates to the 15th century) refers simply to the "action of stretching or enlarging an organ or part of the body."

How to remember the distinction? Try this: the extra syllable in dilatation may strike you as excessive, and sometimes, the presence of that "extra" syllable does indeed suggest something out of the ordinary.