Irregular verbs are verbs whose past tense and past participle forms do not follow the usual -ed pattern. Instead, their forms may change the vowel, change completely, or sometimes stay the same. You need irregular forms mainly for talking about the past and for perfect tenses and passive voice.

You use irregular verb forms in the simple past to describe finished actions or states in the past. You also use the past participle with auxiliary verbs, especially have for perfect tenses and be for the passive. The base form is used for the infinitive, present tense except third person singular, and after modal verbs.

Most irregular verbs are learned through three key forms: base form, simple past, and past participle. The base form appears in dictionary entries and in structures like to go and can go. The simple past is used without an auxiliary in past statements and questions with did. The past participle is used with have or be in perfect tenses and passive constructions.

For irregular verbs, the simple past form must be memorized because it often does not end in -ed. In negatives and questions, English usually uses did plus the base form, so the irregular past form appears mainly in affirmative statements. This is why learners often know the past form but still need to practice where it actually shows up in sentences.

The past participle is the form used with have for present perfect, past perfect, and future perfect. It is also used with be to form the passive voice. Many irregular verbs have a past participle different from the simple past, so you must learn both forms when they differ.

With simple past questions and negatives, English uses did plus the base form, not the irregular past form. This means you say Did you go and not Did you went, and you say I did not go and not I did not went. The irregular past form is used after no auxiliary, as in You went yesterday.

Irregular verbs are not random, and many follow recognizable patterns that help you remember them. Some keep the same form for all three parts, some change only in the past, and some change in both past and past participle. Noticing patterns makes memorization easier and helps you guess forms more accurately.

Word/Phrase	Definition	Example
Same-same-same	Base, past, and participle are identical	put put put
Vowel change	Past changes vowel, participle often matches or differs	begin began begun
Same past participle	Past and participle are identical but differ from base	buy bought bought
Different all	All three forms are different	go went gone

Perfect tenses use have plus the past participle, so irregular participles are essential in these structures. Present perfect connects a past action to now, while past perfect places one past event before another. Using the correct participle is the main challenge with irregular verbs in perfect tenses.

Rule	Example
Present perfect uses have plus past participle	I have seen that movie.
Past perfect uses had plus past participle	She had left before I arrived.
Future perfect uses will have plus past participle	They will have done it by Friday.

Passive voice uses be plus the past participle, so irregular participles also matter here. The passive focuses on the action or result rather than who does the action. You choose the correct tense of be, then add the irregular past participle.

Rule	Example
Passive uses be plus past participle	The window was broken.
Use the correct tense of be for time	The report is written every week.
Add by plus agent only when needed	The song was sung by her.

Because irregular verbs are frequent, learning them in high-use groups gives the best results. Focus on the most common verbs first and always learn them as a three-part set: base, past, participle. Practice them inside the key structures where they appear, especially simple past statements and perfect and passive forms.