"Double letters" means two in a row, like tt in "letter" or oo, kk, and ee in "bookkeeper".
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Aardvark and eel are words. They begin with double letters.
One of the longest words with double letters is "bookkeeper," which has three sets of double letters (oo, kk, ee). Another contender is "bookkeeping," which also features the same double letters. Both words are commonly cited in discussions about words with repeating letters.
Raccoon is a word. It includes double letters in a row.
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Words that have double letters, such as "door" or "glass," can pass through a green glass door.
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