+132.+ We have learned how to form the three principal time forms,
_present_, _past_ and _future_ and the perfect or completed form of each
of the three, _present perfect_, _past perfect_ and _future perfect_.
And still we have such a wonderful language that we can express other
shades of meaning in _time_.
+133.+ There is still another phase of action which we must have a verb
phrase to express. Suppose you want to describe something you are now
doing and are continuing to do, something not yet completed. To say, _I
do it now_, is not satisfactory. Instead we say, _I am doing it now_.
You have by the verb phrase, _am doing_, described a progressive action,
an action _going on_ in the present. You may also want to describe what
you were doing yesterday, an action that continued or _progressed_ in
the past. You would not say, _I built the house yesterday_ but, _I was
building the house yesterday_. Again you may want to describe an action
which will be _progressing_ or going on in the future. You do not say,
_I shall build the house next week_ but, _I shall be building the house
next week_.
So we have progressive verb phrases.
+134.+ +The present progressive describes an action as continuing or
progressing in the present.+
+It is formed by using the present time form of the verb _be_ and the
present participle.+
You remember that the present participle is formed by adding _ing_
to the simple form of the verb.