Here's how it works:
* Verb: I see the dog.
* Past Participle: The dog has been seen in the park.
Past participles can be used in various ways, including:
* Part of a verb phrase: (has been seen)
* As an adjective: (a seen dog)
In the second example, "seen" functions as an adjective describing the dog. However, in the first example, "seen" is part of the verb phrase and not an adjective itself.