The verb "buy" is an irregular verb in English, used to describe the action of purchasing goods or services in exchange for money. In the present simple tense, it is conjugated as "I buy," "you buy," "he/she/it buys," and so on. For example, "They buy groceries every week."

In the past simple tense, "buy" changes to "bought." This form is used to talk about purchases that were made in the past. For instance, "She bought a new car last month."

The past participle of "buy" is also "bought." When forming perfect tenses, such as present perfect or past perfect, the past participle is combined with auxiliary verbs. An example sentence is "They have bought all the necessary equipment."

Understanding the irregular conjugation of "buy" is important for accurately describing actions related to purchasing goods or services. The verb "buy" is also used in various idiomatic expressions, adding to its versatility in the English language.