The present perfect tense connects past actions or states to the present, emphasizing their relevance now. It's formed using the auxiliary verbs "have" or "has" followed by the past participle of the main verb. Use "have" with I, you, we, and they; use "has" with he, she, and it.

Structure:

- Affirmative: [Subject] + have/has + [past participle]
Examples:
- I have finished my homework.
- She has visited Paris.

- Negative: [Subject] + have/has + not + [past participle]
Examples:
- They have not (haven't) seen that movie.
- He has not (hasn't) eaten breakfast.

- Interrogative: Have/Has + [subject] + [past participle]?
- Examples:
- Have you finished the report?
- Has she called you yet?

Uses:

1. Experience: Describes actions or events that occurred at an unspecified time in the past.
- Examples:
- I have traveled to Japan.
- They have never tried sushi.

2. Change Over Time: Highlights changes that have occurred over a period.
- Examples:
- Her English has improved since she moved to London.
- The city has grown rapidly in the last decade.

3. Unfinished Actions: Refers to actions that began in the past and continue into the present.
- Examples:
- We have lived here for five years.
- He has worked at the company since 2010.

4. Recent Actions: Indicates actions that have recently occurred, often with words like "just," "already," or "yet."
- Examples:
- She has just left the office.
- Have you finished your assignment yet?

Note on Time Expressions:

- For is used with periods of time:
- Example:I have known her for ten years.

- Since is used with specific points in time:
- Example: They have been friends since childhood.