A regular verb is one that conforms to the usual rule for forming its
simple past tense and its past participle. A regular verb is any verb whose conjugation follows the typical
pattern, or one of the typical patterns, of the language to which it belongs.
With the exception of the highly irregular verb be, an English verb can
have up to five forms: its plain form (or bare infinitive), a third person
singular present tense, a past tense (or preterite), a past participle, and the
-ing form that serves as both a present participle and gerund.
The rules for the formation of the inflected parts of regular verbs are
given in detail in the article on English verbs. In summary they are as
follows:
•The third person singular present tense is formed by adding the ending
-s (or -es after certain letters) to the plain form. When the plain form ends
with the letter -y following a consonant, this becomes -ies. The ending is
pronounced /s/ after a voiceless consonant sound (as in hops, halts, packs,
bluffs, laughs), or /z/ after a voiced consonant or vowel sound (as in robs,
lends, begs, sings, thaws, flies, sighs), but /ɪz/ after a sibilant (passes,
pushes, marches).
•The past tense and past participle are identical; they are formed with
the ending -ed, which as in the previous case has three different
pronunciations (/t/, /d/, /ɪd/). Certain spelling rules apply, including the
doubling of consonants before the ending in forms like conned and preferred.
There is some variation in the application of these spelling rules with some
rarer verbs, and particularly with verbs ending -c (panic–panicked,
zinc–zinc(k)ed, arc–arced, etc.), meaning that these forms are not fully
predictable, but such verbs are not normally listed among the irregular ones.
(The verbs lay and pay, however, are commonly listed as irregular, despite
being regular in terms of pronunciation – their past forms have the anomalous
spellings laid and paid.)
•The present participle/gerund is formed by adding -ing, again with the
application of certain spelling rules similar to those that apply with -ed.