Here's why:
* Infinitive: An infinitive is the basic form of a verb, usually preceded by "to". In this case, the infinitive is "to finish".
* Infinitive Phrase: An infinitive phrase includes the infinitive and any objects or modifiers that go with it. Here, "mowing the yard" acts as the object of the infinitive "to finish".
Let me know if you have other sentences you'd like to analyze!