A particular subset of fricatives are the sibilants. In Kalaw Lagaw Ya, the palatal consonants are sub-phonemes of the alveolar sibilants and . Rather, first are velar consonants, then coronals, labials, sibilants, etc. A broader category is stridents, which include more fricatives such as uvulars than sibilants. There are many types of postalveolar sounds, especially among the sibilants. The voiceless sibilants, and , are palatalized to and before the front vowels and . There are pharyngealised consonants and a four-way place contrast among sibilants. The exact pronunciation of the three sibilants may vary, but they are distinct phonemes. The second step was the devoicing of voiced sibilants. The post-alveolar sibilants may be whistled. Historically, there was another series of alveolo-palatal sibilants as discussed below. However, the palato-alveolar sibilants in the Northwest Caucasian languages such as Ubykh are an exception. Perhaps most common is the pattern, as in English, with alveolar and palato-alveolar sibilants. The articulation of whistled sibilants may differ between languages. Only a few languages with sibilants lack the hissing type.