I saw this in a grammar book:
Her mother lived to be eighty five.
In this sentence is her mother still alive? Or did she die at 85?
In addition, why does 'infinitive' have such a name? For example, it is easy for me to understand why 'preposition' has such a name or what it means: pre-position locates itself pre noun. Infinitive reminds me of 'infinite, infinity'. ^.^
It is quite likely that her mother has died. The reason for this is that "lived" is a past-tense verb.
The infinitive has nothing to do with the tense of this statement. In fact, an infinitive has nothing to do with tense at all. If we wish, we can express the same sentiment without using an infinitive:
Her mother lived to the age of eighty-five.
If her mother were still living, we would expect a present-tense construction, such as the present perfect:
Her mother has lived for eighty-five years.
There is some ambiguity in the original sentence. The verb uses the past tense, but it also uses the indefinite aspect. This combination of past tense and indefinite aspect is often called the "simple past" or "past simple". This grammatical form places the action of living in the past, but it does not indicate that the action is complete. It can be used for an action that continues to the present.
However, when the simple past is meant to express the imperfect aspect, there is usually something else in the context that indicates an ongoing or incomplete action. Even a simple prepositional phrase can add that context:
Her mother lived for eight-five years so far.
To make the death more certain, we can use a form that marks the act of living as both in the past and finished. This form is the past perfect:
Her mother had lived to be eighty-five.
I said earlier that the infinitive has nothing to do with tense. I take the word "finite" to mean something like having limits or boundaries. I take "infinite" to mean something like an absence of a limit or boundary.
In English grammar and when applied to verbs, "finite" means having boundaries in time. Finite verbs are verbs that are located in the past, in the present, or in the future. Non-finite verbs do not have tense. That is to say, non-finite verbs are not located in the past, in the present, or in the future. They are unbounded in time, just like nouns and prepositions have no location in time.
There are three non-finite forms that are easy to know by name. These are the gerund, the participle, and the infinitive. Even though they do not have tense, the gerund and the participle do show a relationship with time. We use those forms to express aspects, like the perfect aspect or the continuous aspect. The infinitive is the form that is not only unbounded by location in time, but unbounded to any relationship with time. The infinitive is non-finite in more than one way.
Ben Kovitz's answer contains an explanation of what "infinitive" means in Latin grammar, and hints at how it relates to English grammar. We want to use similar terms to describe things in similar ways.
The form that is absolutely unbounded by time, without either tense or aspect, is the best candidate for the name "infinitive".
Her mother died at 85.
It's called the "to-infinitive" because the first word is "to". For example, "Her mother lived to be eighty-five."
The word "infinitive" is taken from Latin. The Romans, when describing Latin grammar, called some of their verb forms modus infinitivus, which means "the indefinite way", because unlike other verb forms, the infinitive ones did not indicate person and number. The infinitive is like an abstract form of the verb. In "John would like to buy some doughnuts", the verb "buy" doesn't agree with John. It names the action of buying without asserting or denying that someone is buying something or specifying a time when the buying happens. That's why the Romans felt that it was "indefinite".
In the sentence "John buys doughnuts during the week", "buy" is called a "finite verb" because it agrees in number with John, it specifies a time when the buying happens, and most importantly of all, it asserts that John buys the doughnuts at that time. The word "finite" comes from Latin finitus, which means limited or bound.* A finite verb is bound—that is, tied to—a subject, about which the verb makes a claim. Finitus comes from the same Latin verb as the English word "finish". You can think of an infinitive verb as "unfinished" in a certain way.
English verbs work very differently from Latin verbs, though. Latin verbs have about 150 different forms, which simultaneously indicate person, number, tense, mood, and voice. English verbs have only a few forms, like buy, buys, bought. The "bare" form of the verb serves many purposes: it's the infinitive, the imperative, the first-person singular and plural, the second-person singular and plural, and the third-person plural. So, English uses subtle tricks to make clear when a verb is meant as an infinitive.
For example, in:
Make John buy me a doughnut.
"buy" is an infinitive. How do you know? You just have to know that the verb make can take a direct object which is the subject of an infinitive verb that follows it. (The infinitive in that sentence has a subject, John, but it doesn't agree in number or person with that subject.) Let and help follow the same pattern.
Modal verbs put the following verb into the infinitive, like this:
John would buy doughnuts if he had enough money.
Don't buy yesterday's doughnuts.
More often, English sticks the word "to" in front of infinitives, which helps make clear that the verb is not being used in a finite way. For example, in:
It's good to be the king.**
You need the "to" to indicate that "be" is to be understood in the abstract. The sentence means the same as "To be the king is good."
Now here is where it starts to get hard—very hard. English also uses the gerund to mean the action of a verb in the abstract, without needing to agree with a subject's person and number. Often you need a verb in such a "non-finite" form to make a combination with another verb, like this:
John meant to buy doughnuts but he forgot to buy them.
John considered buying doughnuts and decided not to buy any.
John imagined buying doughnuts, he dreamed of buying doughnuts, and he wished to buy doughnuts.
In these combined verbs, the first verb is finite and the second verb is either a gerund or a to-infinitive. How do you know whether to use a gerund or a to-infinitive? It depends entirely on the first verb. Some verbs take a gerund and some take a to-infinitive, and there is no rule. As far as I can tell, there is no pattern whatsoever. If you want to feel discouraged, look at this list. You just have to learn one verb at a time, to find out whether it requires a gerund or a to-infinitive when combined with a second verb.
I haven't even told you all of the complexity. I don't know how anyone can possibly learn when to use a to-infinitive, when to use a bare infinitive, and when to use a gerund. Somehow, though, people do. Somehow, native speakers always know which is the correct form. The only thing I can recommend is to have a lot of patience with yourself as you learn. Just imitate what you read and hear, and eventually, somehow, you will find yourself choosing the correct verb form. (Why isn't it "find yourself choose", by analogy with "make yourself choose"? There is no reason.)
*The word "infinite" comes from the "limited" sense of finitus: the Latin roots mean "without limit" or "without end".
**Source: The movie History of the World, Part I.
The infinitive is the base form of a verb.
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The infinitive has two forms:
the to-infinitive = to + base
the zero infinitive = base
The present infinitive base is the verb form you will find in a dictionary.
The to-infinitive is named that way because there is a "to" in front of it, and according to http://www.ucl.ac.uk/internet-grammar/verbs/finite.htm,
Verbs which have the past or the present form are called FINITE verbs. Verbs in any other form (infinitive, -ing, or -ed) are called NONFINITE verbs. This means that verbs with tense are finite, and verbs without tense are nonfinite.
