The perfect tense or aspect (abbreviated PERF or PRF) is a verb form that indicates that an action or circumstance occurred earlier than the time under consideration, often focusing attention on the resulting state rather than on the occurrence itself.
In traditional Latin and Ancient Greek grammar, the perfect tense is a particular, conjugated-verb form.
It should not be confused with the perfective aspect (PFV), which refers to the viewing of an action as a single (but not necessarily prior) event.
The perfect also contrasts with the prospective aspect, which encodes the present relevance or anticipation of a future event.
In English, for example, it can be combined with the progressive (continuous) aspect, wherein an event is viewed as temporary and ongoing.
The have-perfect developed from a construction where the verb meaning have denoted possession, and the past participle was an adjective modifying the object, as in I have the work done.
A vestige of the original interpretation is preserved in some languages in the form of inflection on the participle to agree with the gender and number of the object.
The be-perfect developed similarly, from a construction where the verb meaning be was an ordinary copula and the participle expressed a resultative state of the subject.
The basic (present) perfect form, with the auxiliary in the present tense, may specifically carry the meaning of perfect aspect, as in English; however in some languages it is used more generally as a past tense (or preterite), as in French and German.
Celtic languages (except Cornish and Breton) have a somewhat different type of perfect construction, where a word meaning "after" is used together with a verbal noun.
By analogy with this construction, sentences of the form I'm after eating (meaning "I have eaten") are used in Irish English.
Middle Cornish and Middle Breton used a perfective particle re with the preterite to express a present perfect sense, although this has largely fallen out of use in the modern languages, being replaced with periphrastic formations using the verbs "to be" or "to have" with a past participle.
In reconstructions of the Proto-Indo-European language (PIE), the verb form that has traditionally been called "perfect" in fact signified stative aspect (a current state of being).
The name was assigned based on similarity to the Greek or Latin perfect tense, before the stative nature of the form was fully recognized.
Perfect progressive passives, as in the last example, therefore involve two consecutive participles of the auxiliary verb be; these constructions are rarely used.
The simple past is generally used when the occurrence has a specific past time frame – either explicitly stated (I wrote a book in 1995; the water boiled a minute ago), or implied by the context (for example, in the narration of a sequence of events).