know

The verb "know" is fully irregular — all three principal parts are distinct: the base form "know", the past simple "knew", and the past participle "known". The ABC group contains many of the most common and important verbs in English, so learning them is essential for fluency.

Use the past simple "knew" for actions, events, or states that were completed at a definite point in the past. It is the main verb in the clause and needs no auxiliary: "We knew the whole project in three days." Typical time markers include yesterday, last week, ago, when, and at + a specific time. The past simple is the most frequently used past tense in spoken and written English.

The past participle "known" is never used on its own as a main verb. It appears in: (1) the present perfect with have/has — "I have never known anything like it before"; (2) the past perfect with had — "She had already known before I arrived"; (3) passive voice with a form of be — "The final version was known by the whole team." These three structures together cover the great majority of perfect and passive constructions in English.

The ABC group demands the most memorisation because each verb has three unique forms to learn. Focus first on the highest-frequency verbs: be (was/were/been), do (did/done), go (went/gone), know (knew/known), take (took/taken), see (saw/seen), give (gave/given), and write (wrote/written). Regular reading and listening is the most effective way to make ABC verb forms automatic — passive exposure reinforces the patterns far better than drills alone.