The nominalizer, marks the subject of both transitive and intransitive verbs. In the former case, the tense-aspect of the verb is unspecified, and must be deduced from the context. Thus the sentence “Who is the person who is smoking (or who smokes)” could just as well be translated by the imperfective past as “Who is the person who was smoking? (or who used to smoke?)” or the past perfective, “Who is the person who (has) smoked?”

By contrast, when the nominalizer is used with an intransitive verb, it indicates the present or the future (or else the imperfective past). To indicate the past (perfective) corresponding to the English perfect or preterite, Tibetan uses the nominalizer པ་.

• འགྲོ་མཁན་ “The person who is going, goes, will go, was going”
• བསྡད་མཁན་ “The person who is staying, who stays, will stay, was staying”
• ཕྱིན་པ་ “The person who went, has gone”
• བསྡད་པ་ “The person who stayed, has stayed”