The Tibetan Causative: Phonology

Some written Tibetan causatives differ from their noncausative counterparts through the possession of distinctive prefixes (WT s-nyol-ba, bs-nyal, bs-nyal 'to cause to lie down' : WT nyal-ba, __, __, nyol 'to lie down'). Others differ by both prefixes and the absence of aspiration (WT s-kol-ba, bs-kol, bs-kol 'to cause to boil' : a-khol-ba, khol 'to boil, be boiling'). Yet others, marked by a prefix in the future, have aspiration but lack voicing in the perfect and imperative, in contrast to the noncausative (WT a-bye-d-pa, phye [-d, -s], d-bye; phye [-d, -s] 'to cause to open' : a-bye-ba, bye, ___, bye' to open [by itself]').