Tra từ rarely - Từ điển American Heritage Dictionary 4th

rare·ly (rârʹlē)adv.
1. Not often; infrequently: “The truth is rarely pure and never simple” (Oscar Wilde).
2. In an unusual degree; exceptionally.
3. With uncommon excellence.
Usage Note: Strictly speaking, the use of ever after rarely and seldom is redundant; She rarely ever watches television adds nothing to She rarely watches television. In an earlier survey a large majority of the Usage Panel found this construction unacceptable in formal writing. But ever has been used as an intensive with rarely for several hundred years, and the construction is common in informal contexts. By contrast, the constructions rarely (or seldom) if ever and rarely (or seldom) or never are perfectly acceptable: She rarely if ever watches television. She rarely or never watches television. See Usage Note at hardly. See Usage Note at redundancy.