Intermediate English Grammar for ESL Learners - Robin Torres-Gouzerh 2016

Irregular verbs
3 The verb

Verbs are categorized as irregular when they do not end in -ed in the past tense form. Although there are fewer irregular verbs than regular verbs, they are also among the most commonly used verbs.

The following chart illustrates the various forms of some common irregular verbs. This list is not comprehensive; a complete list can be found in most dictionaries.

The verb be is an exception. Like other verbs, it has a base form (be), a progressive form (being), and a past participle (been). Yet the present tense of be has three distinct forms: (I) am, (he/she/it) is, and (we/you/they) are. Moreover, the past tense of be has two distinct forms: (I/he/she/it) was and (we/you/they) were.