Question 1

How can I tell if "to" is a preposition or part of an infinitive?

Accepted Answer

Try replacing the verb with a noun. If the sentence still makes sense, "to" is a preposition and requires a gerund. "I look forward to the party" makes sense, so in "I look forward to seeing you," the "to" is a preposition — use a gerund. "I want the party" does not mean the same as "I want to go," so in "I want to go," the "to" is part of the infinitive. This test works reliably. Common preposition phrases include "look forward to," "object to," "be used to," "be committed to," and "in addition to." When you learn these phrases, memorise them with gerunds attached.

Question 2

Why do learners often make mistakes with look forward to?

Accepted Answer

Learners make mistakes because they see "to" and automatically think of infinitives — this is called "the to trap." When you learn infinitives first ("want to go," "need to study"), your brain starts to expect "to + base verb" everywhere. But in "look forward to," the "to" belongs to the phrasal verb "look forward to," not to any infinitive. It is a preposition like "of" or "about." Native speakers never say "I look forward to see you" — this sounds clearly wrong. The only way to avoid this mistake is to memorise "look forward to doing" as a complete unit.

Question 3

What other phrases have prepositional "to"?

Accepted Answer

Beyond "look forward to" and "object to," several common phrases use prepositional "to" and require gerunds. "Be/get used to" + gerund means being accustomed to something: "I'm used to working nights." "Be committed to" + gerund means being dedicated: "She's committed to improving her English." "Be opposed to" + gerund means being against something: "They're opposed to building a new road." "Confess to" + gerund means admitting: "He confessed to stealing the money." In all these phrases, you can replace the gerund with a noun, proving "to" is a preposition. This pattern appears regularly in B2 First Use of English.

Gerunds and Infinitives: Look Forward To, Object To

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