In my previous answer, I should have clarified "verb" better to answer your question. A verb shows action, or shows state of being. The first concept you have in Chinese, and although I have some verbal examples, I can't write them for you. I think you'll recognize them, though. I walk. (Walk is the verb. Specifically, it is an "action verb" as it tells what the subject (I) do, did, is doing, etc.) State of being verbs you sort of have in Chinese. You have the concept for state of being verbs with a "predicate nominative" with the Mandarin verb Shi(4). This is the English verb "is" and it's derivatives. English also has a state of being that you do not have in Chinese because you have a different part of speech. In Chinese, your adjectives are state of being verbs. In English, we cannot do this, and must separate out the verb part from the adjective part. So, for example: She is pretty. "she" is the subject. "Pretty" is the predicate adjective, but we cannot use it alone. We must use the state of being verb "is" to indicate her state. "is" is the verb. So a verb is the word indicating what the subject is doing, or tying the state of the subject with another noun (he is a boy) or adjective (she is pretty). Again, hope this helps. It's hard to explain in a few words. :)

The infinitive 'to x' can act as a noun phrase, as a subject or object. The gerund (-ing form) can also do that. He likes to swim in the river. He likes/enjoys swimming in the river. To study is something we should do lifelong. Studying is a lifelong pleasure.

There are a couple of answers at least. First, the infinitive form of the verb in English is the "Dictionary form." Second, an infinitive is a verb that does not serve the purpose of a verb in a sentence. It usually, but not always appears with the word "To" preceding it. It will always be in the infinitive form in English, and this is how you distinguish it from a gerund - gerunds will end in "ing." Example: "Be" is the infinitive form of the verb. Other forms include are, was, and were. The only one of these that can be used with "to" is the infinitive form "Be." When you look it up in the dictionary, "Be" is the base form you look up. An infinitive used in a sentence as a noun: I want to go. Breaking it down: Subject - I Action verb - want Direct object (the thing that is wanted) - to go In this case, the infinitive phrase "to go" occupies the position of direct object, so "to go" is actually a noun. More reading on "infinitive" http://en.wikipedia.org/wiki/Infinitive Summarizing: Infinitive form of a verb is the dictionary form. An infinitive in a sentence is a verb, usually preceded by "to" to form a phrase, that is used as another part of speech like a noun. Hope this helps. Please ask if we need to clarify.