1. As part of the perfect tenses:
* Present perfect: "I have eaten breakfast."
* Past perfect: "She had written the letter before he arrived."
* Future perfect: "They will have finished the project by tomorrow."
2. With auxiliary verbs (helping verbs):
* Passive voice: "The house was built in 1950."
* Modal verbs: "You should have studied harder for the exam."
3. As an adjective:
* "The broken window needs to be repaired."
* "He has a tired look on his face."
4. In participial phrases:
* "Walking down the street, she saw a dog."
* "Having finished her work, she went home."
5. In some set expressions:
* "He was caught red-handed."
* "I'm done with this project."
Key takeaway: The past participle form of a verb indicates a completed action, regardless of the specific tense. It is often used with auxiliary verbs or to modify nouns.