Englishfor English speakers
mutation
Noun
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Any alteration or change.
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A change in genetic material (DNA) which can be passed from parents to children.
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A mutant.
index
Noun
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An index is an alphabetical (A to Z) list, usually at the back of a book, where you can find the pages in a book that talk about particular things or words.
Look in the index to see where they talk about Chomsky.
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An index shows the level of prices, wages, etc. so you can compare them with those of an earlier date.
On Wall Street, the Dow Jones index closed 10 points up at 2,731.23.
index
Verb
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If you index something, you make an index (guide) for it.
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If you index something to a certain price level, you make it go up or down with that level.