Fingerspelling
One of the most striking contact sign phenomena is fingerspelling, in which a writing system is represented with manual signs. In those sign languages where such a system exists, the manual alphabet is structurally quite different from the more 'native' grammatical forms, which are often spatial, visually motivated, and multilayered. Manual alphabets facilitate the input of new terms such as technical vocabulary from the dominant oral language of the region, and allow a transliteration of phrases, names, and places. They may also be used for function words such as 'at', 'so' or 'but'.
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