Habitual aspectIn linguistics, the aspect of a verb is a that defines the temporal flow (or lack thereof) in a given action, event, or state. As its name suggests, the habitual aspect (abbreviated ), not to be confused with iterative aspect or frequentative aspect, specifies an action as occurring habitually: the subject performs the action usually, ordinarily, or customarily. As such, the habitual aspect provides structural information on the nature of the subject referent, "John smokes" being interpretable as "John is a smoker", "Enjoh habitually gets up early in the morning" as "Enjoh is an early bird".
Perfective aspectThe perfective aspect (abbreviated ), sometimes called the aoristic aspect, is a grammatical aspect that describes an action viewed as a simple whole; i.e., a unit without interior composition. The perfective aspect is distinguished from the imperfective aspect, which presents an event as having internal structure (such as ongoing, continuous, or habitual actions). The term perfective should be distinguished from perfect (see below). The distinction between perfective and imperfective is more important in some languages than others.
Do-supportDo-support (periphrastic do or do-insertion), in English grammar, is the use of the auxiliary verb do, including its inflected forms does and did, to form negated clauses and questions as well as other constructions in which subject–auxiliary inversion is required. The verb "do" can be used as an auxiliary even in simple declarative sentences, and it usually serves to add emphasis, as in "I did shut the fridge." However, in the negated and inverted clauses referred to above, it is used because the conventions of Modern English syntax permit these constructions only when an auxiliary is present.
AoristAorist (ˈeɪərᵻst; abbreviated ) verb forms usually express perfective aspect and refer to past events, similar to a preterite. Ancient Greek grammar had the aorist form, and the grammars of other Indo-European languages and languages influenced by the Indo-European grammatical tradition, such as Middle Persian, Sanskrit, Armenian, the South Slavic languages, Georgian, and Pashto also have forms referred to as aorist.
Imperfective aspectThe imperfective (abbreviated or more ambiguously ) is a grammatical aspect used to describe ongoing, habitual, repeated, or similar semantic roles, whether that situation occurs in the past, present, or future. Although many languages have a general imperfective, others have distinct aspects for one or more of its various roles, such as progressive, habitual, and iterative aspects. The imperfective contrasts with the perfective aspect, which is used to describe actions viewed as a complete whole.
Irrealis moodIn linguistics, irrealis moods (abbreviated ) are the main set of grammatical moods that indicate that a certain situation or action is not known to have happened at the moment the speaker is talking. This contrasts with the realis moods. Every language has grammatical ways of expressing unreality. Linguists tend to reserve the term "irrealis" for particular morphological markers or clause types. Many languages with irrealis mood make further subdivisions between kinds of irrealis moods.
Conditional sentenceConditional sentences are natural language sentences that express that one thing is contingent on something else, e.g. "If it rains, the picnic will be cancelled." They are so called because the impact of the main clause of the sentence is conditional on the dependent clause. A full conditional thus contains two clauses: a dependent clause called the antecedent (or protasis or if-clause), which expresses the condition, and a main clause called the consequent (or apodosis or then-clause) expressing the result.
Isolating languageAn isolating language is a type of language with a morpheme per word ratio close to one, and with no inflectional morphology whatsoever. In the extreme case, each word contains a single morpheme. Examples of widely spoken isolating languages are Yoruba in West Africa and Vietnamese (especially its colloquial register) in Southeast Asia. A closely related concept is that of an analytic language, which uses unbound morphemes or syntactical constructions to indicate grammatical relationships.
TelicityIn linguistics, telicity (tiːˈlɪsɪti; ) is the property of a verb or verb phrase that presents an action or event as having a specific endpoint. A verb or verb phrase with this property is said to be telic; if the situation it describes is not heading for any particular endpoint, it is said to be atelic. One common way to gauge whether an English verb phrase is telic is to see whether such a phrase as in an hour, in the sense of "within an hour", (known as a time-frame adverbial) can be applied to it.
Realis moodA realis mood (abbreviated ) is a grammatical mood which is used principally to indicate that something is a statement of fact; in other words, to express what the speaker considers to be a known state of affairs, as in declarative sentences. Most languages have a single realis mood called the indicative mood, although some languages have additional realis moods, for example to express different levels of certainty. By contrast, an irrealis mood is used to express something that is not known to be the case in reality.
