Particle or preposition

[ltrevor]

I understand that in the below sentence "catch on" is a phrasal verb in that it's meaning is not literal but idiomatic, further more, that "catch" is the base verb and "on" is the particle.
My problem is, a preposition needs a noun or pronoun to follow it (the object of a preposition) otherwise it's function is that of a particle or an adverb.

how is the word "to" named in this example sentence:

"He began to catch on.
An explanation of why would be most appreciated.
Thank you in advance.

[Maeve]

Trevor,

"to catch on" is the infinitive form of a verb. The "to" is not a separate part of speech. It goes with the infinitive.

Maeve

[rdwriter]

Ditto what Maeve said. :)