Page 84 - Just Enough English Grammar Illustrated Book

The vast number of nouns you could choose as subjects is too
big for this book. However, verbs can also connect to pronouns.
Since you know how to replace nouns with pronouns, we will
simplify the presentation of the principal parts of verbs by using
pronouns for most of the examples.

In Part Two you will learn that verbs show time. We have covered
the verb form used to make general statements. It is identical
to the base form of the verb except that we had to make a small
change for the third-person singular. The principal part that we
will look at next is a verb form that expresses action that took
place in the past.

4.7 The Second Principal Part: Past Form
It is a good practice to always start with the base form of a verb.
Both regular and irregular verbs can show changes in their
forms. The changes for regular verbs build on the base form,
and these changes are easily recognized. When irregular verbs
change their form, however, the base form can be very hard to
detect. Therefore, it is essential for beginners to learn the base
form of verbs.
Principal Part is the past form of verbs. The following
examples illustrate changing from the base form to the past
form of both regular and irregular verbs.

I walked Base form: walk
to the school. The past form of a regular verb follows
a pattern: Add -ed to the base form
of the verb.

Base form: write
I wrote
a book. The past form of an irregular verb
follows no apparent pattern: The past
form must be memorized.

Regular verbs follow a set pattern of adding “-ed”
to the base form when forming the past form of a verb.

Here are examples of the base form and past form of three
regular verbs: fix ~ fixed, match ~ matched, learn ~ learned.
Note these spelling changes when adding the suffix -ed:
study ~ studied, trim ~ trimmed.
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