Sign languages such as American Sign Language (ASL) are characterized by phonological processes analogous to, yet dissimilar from those of oral languages. Although there is a qualitative difference from oral languages in that sign-language phonemes are not based on sound, and are spatial in addition to being temporal, they fulfill the same role as phonemes in oral languages.
Basically, three types of signs are distinguished: one-handed signs, symmetric two-handed signs (i.e. signs in which both hands are active and perform the same or a similar action), and asymmetric two-handed signs (i.e. signs in which one hand is active [the 'dominant' or 'strong' hand] and one hand is held static [the 'non-dominant' or 'weak' hand]). The non-dominant hand in asymmetric signs often functions as the location of the sign. Almost all simple signs in ASL are monosyllabic.