How is the infinitive phrase used in the sentence, "He wants to tell you about his day."?
It is used as a direct object.
To begin with, what is an infinitive ?
- An infinitive is "to + a verb". In infinitive phrase begins with the infinitive, and contains any complements or modifiers.
So where is it in our sentence? I highlighted it for you:
To find what part of speech it is, let's find the subject and verb of the sentence:
Now ask yourself: "What does he want?"
The answer: "To tell you about his day".
Since the infinitive phrase "to tell you about his day" answers the question "what", it is a direct object. It is receiving the "want" of the subject he.
This is a good video on direct objects: