Bruxism bruxism), but also possibly grinding, and is often associated with other semivoluntary oral habits such as cheek biting, nail biting, chewing on a pen or pencil absent mindedly, or tongue thrusting (where the tongue is pushed against the front teeth forcefully). There is evidence that sleep bruxism is caused by mechanisms related to the central nervous system, involving sleep arousal and neurotransmitter abnormalities. Underlying these factors may be psychosocial factors including daytime stress which is disrupting peaceful sleep. Sleep bruxism is mainly characterized by "rhythmic masticatory muscle activity" (RMMA) at a frequency of about once per second, and also with
Habitual aspect Italian, and Portuguese do not have a grammatical form that is specific to the habitual aspect. In the past tense, they have a form called the imperfect, which combines the past tense with the imperfective aspect; it is used to indicate that a past ongoing process was habitual or continuous. Cantonese, a Sinitic language, has a dedicated particle to express the habitual aspect, 開 "hoi1", which follows the verb. This is unlike Mandarin and some other Sinitic languages, which have no grammatical indicators of the habitual aspect, but may express habituality via circumlocution. Habitual aspect In linguistics, the aspect of