Friday, June 8, 2012

English Verb System

Back 20 years ago now, I took a natural language processing class.  Overall the class was excellent and it really taught me a lot about how languages work.  One handout in particular was useful to me.  The instructor had us do simple verbs at first, and that worked great, but then we had to start parsing helper verbs and the instructor gave us a sheet that he had copied out of a book: Summary of the verb system in A Student's Grammar of the English Language, by Greenbaum and Quirk, Longman Publishers, 1990.

CS 469B/569B
Natural Language Processing - 1992
Cem Bozsahin

English Verb System

English verbs can be characterized by
  1. Form
  2. Tense
  3. Auxiliary (optional)
constructions.  The table below shows the classifications based on form and tense.

Form Name
Regular Example
Irregular Example
base
work
go
s
works
goes
ing
working
going
past
worked
went
past-participle
worked
gone

Tense Name
Number of Subjects
Verb Form
Example
present
3rd person singular
s
he sings
present
others
base
they sing
past
all
past
he sang

Auxiliary constructions may proceed a verb.  The first auxiliary (if present) carries the tense in English.  Their ordering is as follows (parentheses mean optional items):

(modal) (perfect) (progressive) (passive) main-verb

For example, he would have sung has two auxiliaries (would and have), the main verb is sing and the tense is past (would is the past form of will).

If no auxiliary is present, the verb carries the tense (e.g., he sang).  Below is a list of auxiliary verbs:

type
base form
past form
past-participle form
modal
will, can, shall, may, must
would, could, should, might

perfect
have, has
had

progressive
be (is, am, are, be)
be (was, were, be)
been
passive
be (is, am, are, be)
be (was, were, being)
been

The combinations of perfect and progressive is called the aspect of the main verb.  Below is the list of possible combinations:

aspect
comment
example
simple
no perfect or progressive
he sang
perfect
perfect only
he has sung
progressive
progressive only
he was singing
perfect-progressive
both perfect and progressive
he has been singing

The presence of an auxiliary verb signals the form of the next verb as well.  In the table below, a verb type in the first column is supposed to be followed by a verb form in the second column:

aux verb
form of the next verb
example
modal
base
he will go home
perfect
past-participle
he has written two papers
be(progressive)
ing
he was singing a song
be(passive)
past-participle
it was brought to Mary by John
do
base
I did go to the theater
no aux
base or ing
to err is human (base)
playing piano is fun (ing)