present perfect

The present perfect tense is used to describe actions or situations that have occurred at some point in the past but are relevant to or have an impact on the present. It is formed using the auxiliary verb "have" (or "has" for he, she, it) followed by the past participle of the main verb.

### Structure
- **Affirmative:** Subject + have/has + past participle  
  Example: "I have visited Paris."

- **Negative:** Subject + have/has + not + past participle  
  Example: "She has not seen that movie."

- **Interrogative:** Have/Has + subject + past participle?  
  Example: "Have you finished your homework?"

### Common Uses
1. **Unspecified Time in the Past:**  
   The exact time is not important.  
   Example: "They have traveled to Japan."

2. **Life Experiences:**  
   Experiences that are relevant to the present.  
   Example: "I have never eaten sushi."

3. **Changes Over Time:**  
   To express changes that have taken place.  
   Example: "Her English has improved."

4. **Completion of Actions:**  
   It may indicate that something has been completed recently or at some point before now.  
   Example: "He has just finished his report."

5. **Repeated Actions:**  
   Actions that have occurred multiple times up to now.  
   Example: "We have gone to that restaurant several times."

### Signals of Present Perfect
- Adverbs such as "already," "yet," "just," "ever," and "never" are often used with the present perfect tense.

### Examples
- "I have known her for years."
- "They have just arrived."
- "Has she ever been to Canada?"

If you have any specific questions about the present perfect tense or need examples, feel free to ask!