|1. They add -s to form the 3rd person present singular.|
|2. The past participle and simple past tense are formed by adding -ed.|
|3. The present participle is formed by adding -ing.|
There are well over 300 verbs which do not obey one or more of these procedures. Space precludes listing them all; besides, I think that would be tedious rather than helpful-both to read and to write. What is worthwhile is to look at the various kinds of irregular verb, with examples of each.
A. A number of verbs seem to be entirely regular, but they incorporate a change of spelling in one or more of their forms. For example:
(a) stop takes a double p in both participle forms and in the simple past:
(b) So does hop: