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The shape and length of the apex can vary, sometimes within a single inscription. While virtually all apices consist of a line sloping up to the right, the line can be more or less curved, and varies in length from less than half the height of a letter to more than the height of a letter. Sometimes, it is adorned at the top with a distinct hook, protruding to the left. Rather than being centered over the vowel it modifies, the apex is often considerably displaced to the right.
Essentially the same diacritic, conventionally called in English the acute accent, is used today for the same purpose of denoting long vowels in a number of languages with Latin orthography, such as Irish (called in it the síneadh fada [ˈʃiːnʲə ˈfˠɑd̪ˠə] or simply fada "long"), Hungarian (hosszú ékezet [ˈhosːuː ˈeːkɛzɛt], from the words for "long" and "wedge"), Czech (called in it čárka [ˈtʃaːrka], "small line") and Slovak (dĺžeň [ˈdɫ̩ːʒɛɲ], from the word for "long"), as well as for the historically long vowels of Icelandic. In the 17th century, with a specialized shape distinct from that of the acute accent, a curved diacritic by the name of "apex" was adopted to mark final nasalization in the early Vietnamese alphabet, which already had an acute accent diacritic that was used to mark one of the tones.