And anal English speakers (such as the copy editors of the New Yorker) also use the diaresis (the double dot over a vowel). In English, it is used over the second of two vowels in a row which are voiced separately, such as naive (should have the double dot over the i) or cooperate (double dot over the second o). The distinction is between a word like coop (meaning a house for chickens) in which the two vowels make one sound and a word like cooperation, in which the two o&#x27;s are separate sounds.