رضا: That site of Marfitalu's is in Canadian English. Perhaps they use it differently there? I know when I've travelled there some words are pronounced differently.

I'd say your book has it right, and it agrees with Marfitalu's and my use of the words when it comes to buying bread and bringing it home for the missus.

What's an infinitive? n. A verb form expressing action or condition without reference to person, tense, or number, as "to run". In English, its sign "to" is omitted after most auxiliaries, as in, "He should 'go' now," but is retained when the infinitive functions as a noun, as in "'To ride' horses was his favorite sport."

I'd be hard pressed to give you an example of an infinitve and feel positive that I was right from this definition! :)
English must be one hard language to learn. Somehow I missed all this and learned without it. I have the feeling some of you 'English as a Second Language' people probably have better English skills than some native speakers, though in reza's case it might be because he's an English teacher.