Are infinitives always preceded by the word "to"?
What I mean is, is the "to" ever just understood in the phrase?
Infinitives are always preceded by the word "to" and to get the infinitive, try to change the verb to a form that makes sense with "to", when it is placed in front of it. Always avoid placing "to" before an infinitive in modal auxiliaries.
The infinitive of a verb, in English, will always be preceded by "to", yes