What is the easiest way to understand what an infinitive is?
How do I know which verb in which sentence is an infinitive?
For example, let us take this website:
This is the example I am interested in:
- I need to run every day. (The infinitive form with the word to is called the full infinitive or to-infinitive.)
- I must run every day. (After certain verbs, the to is dropped (more on this below).)
- I run every day. (This is not in the infinitive form. This is a finite verb, i.e., a verb functioning as the main verb.)
How do I differentiate between example 2 and example 3?
How do I know 3 is not an infinitive but 2 is ?
If 2 had been I must run to school every day would that make it a non-infinitive?
This is probably a completely different question, but I will put it here anyway.
When comparing with other languages, if it says infinitive, should I consider it to have the same meaning as the English infinitive, or can it have a different meaning, according to the language?
Let us take the example of Korean. This Wikipedia page has an entry for infinitives in Korean. If I understood correctly, "infinitive" is the form of the verb that is unchanged according to tense, voice or anything similar. (So watch may be an infinitive but watched is not). In Korean, the unchanged form of a verb is called root (example, watch = 보다). This root changes form (prefixes, suffixes etc, based on negation, formality, tense, etc). Can this root be called an infinitive as well? (in my opinion, probably not, as the explanations in the wikipedia page I linked seems to use root and infinitive as different entities, but how do I explain the difference)?