From what I know, bare infinitive just removes the preposition from the verb itself. I am presuming that you already know what these infinitives are, but don't know of examples. If you don't know what infinitives are or how to use them, then I'd say your foundation for English needs to be reworked (these are relatively simple concepts in my opinion, meaning that they are concepts that any intermediate English student should know). Then the difference between infinitives using one example (verb): Infinitive = "to break" Present infinitive = "break" (I can't imagine it being anything else because I have never heard of an infinitive being present... either it's an infinitive, or it's not. Infinitives by default do not have a time attachment. I'm not actually sure where or who told you about this "present infinitive" concept.) Perfect infinitive = "broken" There are more details to this, though. So, if you want a more clear explanation, do ask.

The form without to is called the bare infinitive More info http://www.englishpage.net/showthread.php?1451-Present-Perfect-Tense-Bare-Perfect-Infinitive http://english.stackexchange.com/questions/53562/subject-have-had-bare-infinitive-ever-correct