to [verb] -- is the full infinitive. It is the "name" of the verb. It can function as:
a noun: To be or not to be, that is the question (subject). I want to go home. (direct object).
an adverb: I am doing it to help you (answers the question: why). That is very hard to do (describes the adjective hard)
an adjective: That's the thing to do (describes the thing).
v + [ing] - is two different forms that look identical:
the "present" participle: used to form:
the progressive aspect in various tenses and modal constructions: I am doing that. He was doing that. They might have been doing that.
an adjective: the dining room (dining, from dine)
to replace a dependent clause when it has the same subject as the main clause: Realizing his parents had
discovered the truth, he decided to confess. (Because he realized his parents had discovered...)
the gerund - functions as a noun. I like listening to music. Listening to music is fun. She can't eat without brushing her teeth first.
note: the gerund and the infinitive can both be nouns. Technically, both should be possible, and often are. Sometimes, though, only one form sounds natural (just have to learn those).
I like listening to music. I like to listen to music. -- both okay. BUT: I want to go home (not: I want going home).
Note: the modal auxiliary verbs are "defective", in the sense that they are only helping verbs and do not have all possible forms. can, could, may, might, shall, should, will, would, must, ought to, etc.
The other three frequent helping verbs in English are have/do/be, which can each also be a main verb, and do have both forms (to be, being; to have, having) etc.
I cannot think of an example where you can use either form, but with different meanings. (There may be some, but I can't think of them right now). That could only happen when they are functioning as the same part of speech. (note that the full infinitive and the gerund, although formed from verbs, function as other parts of speech, as noted above. The present participle, also as noted, sometimes is part of verb structure, and sometimes not).
Answers & Comments
Verified answer
All full fledged verbs have both forms.
to [verb] -- is the full infinitive. It is the "name" of the verb. It can function as:
a noun: To be or not to be, that is the question (subject). I want to go home. (direct object).
an adverb: I am doing it to help you (answers the question: why). That is very hard to do (describes the adjective hard)
an adjective: That's the thing to do (describes the thing).
v + [ing] - is two different forms that look identical:
the "present" participle: used to form:
the progressive aspect in various tenses and modal constructions: I am doing that. He was doing that. They might have been doing that.
an adjective: the dining room (dining, from dine)
to replace a dependent clause when it has the same subject as the main clause: Realizing his parents had
discovered the truth, he decided to confess. (Because he realized his parents had discovered...)
the gerund - functions as a noun. I like listening to music. Listening to music is fun. She can't eat without brushing her teeth first.
note: the gerund and the infinitive can both be nouns. Technically, both should be possible, and often are. Sometimes, though, only one form sounds natural (just have to learn those).
I like listening to music. I like to listen to music. -- both okay. BUT: I want to go home (not: I want going home).
Note: the modal auxiliary verbs are "defective", in the sense that they are only helping verbs and do not have all possible forms. can, could, may, might, shall, should, will, would, must, ought to, etc.
The other three frequent helping verbs in English are have/do/be, which can each also be a main verb, and do have both forms (to be, being; to have, having) etc.
I cannot think of an example where you can use either form, but with different meanings. (There may be some, but I can't think of them right now). That could only happen when they are functioning as the same part of speech. (note that the full infinitive and the gerund, although formed from verbs, function as other parts of speech, as noted above. The present participle, also as noted, sometimes is part of verb structure, and sometimes not).