Some terms grammarians use for expressions such as have to
and need to are: "near modals," "quasi-modals,"
"semi-modals," or "marginal modals," which all show
how close in meaning they are to the true modals.
It's logical and helpful to teach these near-modals together with the
true modals. It makes the meaning of the true modals quite clear. In
fact, in some cases, learners need to know the forms the near-modals
right along with those of the “true modals.” An example
of this is have to, which really has to be/ must be
learned at the same time as must. See Marilyn's reasoning
Have to is one of the most useful verbs in the English
language and should be taught early, as a main verb. It resurfaces in
an important role when the modal must is taught. Whereas
must, in its meaning of strong obligation, occurs in
affirmative statements, the negative and interrogative forms require
have to, as in (b) and (c) below:
||Passengers must show ID when boarding
||Do passengers have to show their
ticket receipts when boarding the plane?
||Passengers do not have to show their ticket receipts
when boarding the plane.
Furthermore, since must is not generally used in independent
clauses in the past, (but it is used in subordinate
clauses), learners need to know that it's necessary to use had
to. Compare (d) below, a statement about the present and future,
and (e), a statement about the past:
||When a player's contract is up, he must
receive a new offer that equals the old.
||Under the old arrangement, when a player's contract was up, he
had to receive a new offer that equaled the old.
(adapted from the online Collins COBUILD Concordance Sampler)
Have to combines freely with the “true”
modals, as in “You'll have to take a later
flight “or “He shouldn't have to choose
his major so soon.” Therefore, and also because it is such
a useful and necessary verb to know for communication, have
to is an important verb for learners to know early. At a more
advanced stage, they can profitably learn have got to.
Need to can and should be taught as a main
verb, not a kind of modal. Need to has all
the features of the main verb need, including marking
for person and tense, as well as do-support for negatives and questions.
It also carries lexical meaning: there is no difference in meaning between
the two needs in “I need
a vacation” and “I need to take
a vacation.” Or between “Your hair needs
cutting” and “Your hair needs
to be cut.”
The “true” modal need, followed by the
bare infinitive, e.g., You need look no further, is restricted
to hyperformal style and occurs almost exclusively in negative statements.
It is therefore of little use to lower-level learners. It can be taught
to advanced learners who will be reading texts in which it can be expected
I should point out that need to does have a pragmatic,
or practical, relation to should and ought
to. In face-to-face interactions, need to
is often a less threatening way to give advice or directives. Compare:
||You should use a finer grade of sandpaper
on that fender
||You ought to use a finer grade of sandpaper on
||You need to use a finer grade of sandpaper on
The use of need to in (h) is less authoritarian than
should in (f) or ought to in (g),
and would be useful for ESL learners who are actually going to interact
with native speakers and who might be perceived as too aggressive if
they use should or ought to. Usually this kind of
information in EFL (as opposed to ESL) courses can be deferred to the
Be supposed to has several meanings—mild
obligation and expectation among them. In this respect it resembles
should and ought to. It does not, however, share any
of the grammatical features of modals, and does not figure in any of
the permutations of modals, as does have to.
Be supposed to is a member of a rather large group of verbs
known as semi-auxiliaries (not quasi-modals, near-modals, semi-modals,
or marginal modals), including be able to, be about to,
be going to, be likely to, and be willing to (from Quirk et
al., A Comprehensive Grammar of the English Language, Longman,
1985). These verbs should be taught as needed. The resemblance in meaning
between be supposed to and should/ought to (especially in the
past) can be taught at a later stage.