* Past participle of the verb "to see": This is the most common use of "seen." It acts as an adjective, describing something that has been perceived by sight.
* Example: "I have seen the Eiffel Tower."
* Part of a present perfect tense: This is used when the action of seeing happened in the past and continues to have a present effect.
* Example: "I have seen that movie many times."
* Part of a passive voice sentence: This is used when the subject is acted upon by something else.
* Example: "The painting was seen by millions of people."
To determine the part of speech, you need to analyze the context in which "seen" is used.