Verb Primer

Basic verb terminology

Finite vs. Non-finite verbs
Verbs are either finite or non-finite. We speak of finite verb forms and non-finite verb forms. One type of non-finite verb form is the infinitive (more on this below). Note that we do NOT have "infinite" verb forms. We have infinitives or non-finite forms.
Finite forms are forms that have tense. English is a morphologically poor language, so we only see tense in the past tense and in the third person singular present tense (she runs). Many other languages mark many more things on their verbs.

English has several non-finite forms of the verb:
bare stems, which follow modals, e.g., I can walk.
infinitive forms: I like to walk
participials: present participle: -ing, as in I am walking or past participle: I have walked/I have eaten.

Tense, Aspect, and Voice
Tense: Tense encodes notions of time.  So, we can talk about past tense (in English: walk-ed) or present tense (English: walk-s). Some languages have a future tense. (English does not mark future morphologically.) Tense is associated with a clause and not with an individual verb. So, we talk about finite (tensed) clauses and non-finite clauses.

Aspect: Aspect encodes information about the way in which the action expressed by the verb is perceived, e.g., is it still on-going (progressive, English: is walking) , has it started in the past and continues up to the present (perfective, English: I have walked). English marks aspect by a combination of auxiliary verbs (be or have) and markings on the main verb (-ing, or -en/-ed).

Voice: Grammatical encoding of the syntactic roles of the units related to the verb. In modern English, we distinguish between active and passive voice. Samantha hexed Darrin is active voice. Darrin was hexed (by Samantha) is passive voice. In active voice, the agent tends to be the subject and the theme the object. In passive voice, the agent is no longer present and the theme becomes the grammatical subject (but retains its theme role).

We can have a clause that combines these features of tense, aspect and voice:
I think that [I am walking the dog]. Here the subordinate clause is tensed, in present progressive aspect and active voice.
I want [to be walking the dog.] Here the subordinate clause is non-tensed (non-finite), present progressive and active.
The dog wants [to be being walked]. Here the subordinate clause is non-tensed, present progressive and passive.

Case: Case is grammatical marking that occurs on NOUNS. So, why are we talking about it in a primer on verbs? Because verbs ASSIGN case. Nouns GET case. Case marks the relationship of the noun to the verb. We speak of morphological case (case you can see) and abstract Case, which is the abstract relationship between the noun and the verb or preposition. In terms of morphological case, nominative case generally marks subjects. Accusative case usually marks direct objects or objects of some prepositions. Dative case marks indirect objects or objects of other prepositions. Genitive case generally marks possession. English only marks case on pronouns and distinguishes between subject and object case, as well as genitive. Many other languages have more cases than just these and many mark them on full nouns.

Case and Tense: Object case is associated with the main verb. So in : Darrin eats bananas, the verb eats assigns object case to the noun: bananas. Object case can be assigned whether or not the verb is finite. So, you can say: Darrin wants to eat bananas. "eat" still assigns object case here.

Subject case (nominative) is associated with and assigned by T. In English, only finite T can assign nominative case. The DP must move to Spec,TP to receive this case. So, in Darrin wants to eat the bananas, the finite T above 'wants' assigns case to Darrin ('wants' itself does NOT assign Case to Darrin, only the theta role). 'eat' is non-finite however and assigns no case to its subject position.

Case and Voice: Passive voice affects what cases can be assigned. Passive does two things: It absorbs the agent theta role and it removes the ability of the main verb to assign object case. Passive main verbs cannot assign accusative case. *was eaten the bananas. Therefore, the object needs to move to get case ==> The bananas were eaten. Note: This has absolutely nothing to do with the TENSE of the verb. It's the VOICE that affects the ability to assign acc. case.

Person and Agreement
Person: Is a grammatical category that distinguishes speakers and addressees from one another and from other individuals. Traditionally, forms referring to the speaker are first person (I, we, we'all), forms referring to the addressee are second person (you, y'all), and forms referring to someone not present are third person (he, she, it, they, them). Person can be marked on verbs as part of agreement.

Agreement: marks a syntactic relation between words and phrases. So, in most Indo-European languages, verbs agree with their subjects (Latin: amo 'I love' amas 'you-sg love' amat 'he loves', etc.). Some languages also have object agreement, where the object agrees with the verb. Some languages mark the gender of the subj/object as well as the person. Agreement can also take place between determiners and nouns (these books, this book).

Verb movement
Main verbs in English (those with lexical content) do NOT undergo raising. You can see this by the following sentence:

I often eat chocolate.
I often read syntax.
I do not love eggplant.
I do not read romance novels.

In each case the main verb ('eat' or 'read') appears to the right of the adverb or negative, indicating that it has not moved.

Auxiliary verbs in English and Copula be DO move, IF they are finite. How can we tell?  In finite constructions, they appear to the LEFT of the adverb:

I am often eating chocolate.
I am often reading syntax homework.
I am not crazy.
She has not read too enough syntax.

In non-finite constructions, however, they appear to the RIGHT of the adverb:
I will often be eating chocolate.
I have often been reading syntax homework.
I might not be crazy.
She can not have read enough syntax.

The easiest way we can account for the alternation in position between the finite forms of these verbs ('am', 'is' 'are', 'were' 'has') and the non-finite forms ('be', 'been', 'have' etc.) is to posit raising for these verbs from V to T.

Modals and auxiliary do do not undergo V to T raising. They start off in T.
The infinitive marker 'to' also starts in T. It is NOT a verb itself, but part of the verb phrase. Do not confuse the infinitive 'to' with preposition 'to'. They are homophonous, but do very different things.

Summary of verb types
Start in V, never Raise
Require insertion of auxiliary do for negation or question formation
Start in V, take VP as complement
Raise from V to T if finite. 
Can raise T to C in questions.
Start in T, take VP as complement. 
Can raise T to C in questions. 
Main verbs
e.g., eat, sleep, see, feel, walk, gnash, regurgitate, etc.
Auxiliary Verbs, Copula be
is (and all its forms)
have (and all its forms)
Modal verbs
e.g., can, could, will, would, may, might, ought, etc. 
Auxiliary do