In linguistics, a pro-verb is a verb or partial phrase that substitutes for a contextually recognizable verb phrase (via a process known as grammatical gapping), obviating the need to repeat an antecedent verb phrase. A pro-verb is a type of anaphora that falls within the general group of word classes called pro-forms.
English does not have dedicated pro-verbs; however, a bare infinitive can generally be implied rather than expressed, such that the verbs that take bare infinitives (including most of the auxiliary verbs) can be said to double as pro-verbs. Additionally, have and be can double as pro-verbs for perfect, progressive, and passive constructions (by eliding the participle). Finally, the dummy auxiliary verb do can be used when there is no other auxiliary verb, except if the main verb is be. The following are some examples of these kinds of pro-verb:
Note that, when there are multiple auxiliary verbs, some of these may be elided as well. For example, in reply to "Who's been leaving the milk out of the refrigerator?", any of "You've been doing it", "You have been", or "You have" would have the same meaning.
Since a to-infinitive is just the particle to plus a bare infinitive, and a bare infinitive can be elided, the particle to doubles as a pro-verb for a to-infinitive:
Finally, even in dialects where bare infinitives and participles can be elided, there does exist the pro-verb do so: "He asked me to leave, so I did so". This pro-verb, unlike the above-described pro-verbs, can be used in any grammatical context; however, in contexts where another pro-verb could be used, it can be overly formal. For example, in "I want to get an 'A', but to do so, I need to get a perfect score on the next test," there is no other pro-verb that could be used; whereas in "I want to get an 'A', but I can't do so," the do so could simply be elided, and doing so would make the sentence sound less formal.