<P> There are two families of manual alphabets used for representing the Latin alphabet in the modern world . The more common of the two is mostly produced on one hand, and can be traced back to alphabetic signs used in Europe from at least the early 15th century . The alphabet, first described completely by Spanish monks, was adopted by the Abbé de l'Épée's deaf school in Paris in the 18th century, and was then spread to deaf communities around the world in the 19th and 20th centuries via educators who had learned it in Paris . Over time, variations have emerged, brought about by natural phonetic changes that occur over time, adaptions for local written forms with special characters or diacritics (which are sometimes represented with the other hand), and avoidance of handshapes that are considered obscene in some cultures . The most widely used modern descendant is the American manual alphabet . </P> <P> Two - handed manual alphabets are used by a number of deaf communities; one such alphabet is shared by users of British Sign Language, Auslan and New Zealand Sign Language (collectively known as the BANZSL language family), while another is used in Turkish Sign Language . Some of the letters are represented by iconic shapes, and in the BANZSL languages the vowels are represented by pointing to the fingertips . </P> <P> Letters are formed by a dominant hand, which is on top of or alongside the other hand at the point of contact, and a subordinate hand, which uses either the same or a simpler handshape as the dominant hand . Either the left or right hand can be dominant . In a modified tactile form used by deafblind people, the signer's hand acts as the dominant hand, and the receiver's hand becomes the subordinate hand . </P> <P> Some signs, such as the sign commonly used for the letter C, may be one - handed . </P>

What two letters in american sign language require a finger movement