Please explain the usage of have, has and had respectively with clear examples.

Sure! "Have," "has," and "had" are all forms of the verb "to have" and are used in different contexts. Here are their usages with clear examples:

1. Have:
- "Have" is the base form of the verb and can be used with first person (I, we), second person (you), or plural third person (they).
- It is used to indicate possession, ownership, or to describe actions in the present tense. Examples:
- "I have a car." (possession)
- "We have a meeting at 2 pm." (action)
- "You have a great talent!" (compliment)
- "They have three children." (possession)

2. Has:
- "Has" is the third person singular form of the verb and is used with singular third person pronouns (he, she, it) or singular nouns.
- It also indicates possession, ownership, or describes actions in the present tense. Examples:
- "She has a cat." (possession)
- "He has an appointment with the doctor." (action)
- "The company has a strict policy." (possession)
- "The dog has a bone." (possession)

3. Had:
- "Had" is the past tense form of the verb and is used to indicate past actions or possession.
- It is used with all persons and numbers and can be used as a main verb or as an auxiliary verb in forming the past perfect tense. Examples:
- "I had a nice vacation last year." (past action)
- "She had two cups of coffee this morning." (past action)
- "We had a great time at the party." (past action)
- "He had already finished his homework when I arrived." (past perfect)

Remember that the usage of these forms can vary based on the context and the tense being referred to.