+168.+ We have found that whenever a verb is used by itself in making an
assertion it denotes either present or past time. When we use a verb
phrase, it expresses some other time than the past or present. These
verb phrases are formed by using _shall_, _will_, _have_, _had_, and the
various forms of the verb _be_ with some form of the principal verb.
These verbs which help to form verb phrases are called _helping_, or
_auxiliary verbs_. Auxiliary means helping.
We have used _have_ and _had_ with the past participle to form the
present perfect and past perfect time forms. We have used _shall_ and
_will_ with different forms of the verb to denote future time, and we
have used different forms of the verb _be_ in making the various other
time forms. So _shall_, _will_, _have_, _had_ and the various forms of
the verb _be_ are _helping verbs_, which we use to help us in making
verb phrases.
+169.+ But these are not all of the helping verbs. There are other
helping verbs which we use in forming verb phrases to express different
ideas. These are such verbs as _should_ and _would_, _may_ and _might_,
_can_ and _could_, _must_ and _ought_, _do_ and _did_.