The forms of a verb which have a tense are called finite forms. Participles (ending in ‘-ing’ and used as adjectives), gerunds (also ending in ‘-ing’, but used as nouns), and infinitives (such as ‘go’ or ‘to go’), however, do not in their own right have tenses. These verb forms are described as non-finite.

Any sentence is composed of one or more clauses. At least one of these clauses must be a Main Clause, which can stand on its own without the rest of the sentence. Every clause in a sentence includes one and only one finite verb.

‘Jackie hit the ball’ is a main clause, and makes sense on its own as a sentence.

‘Jackie, hitting the ball …’ is not a sentence. It has no finite verb and hence no tense. This clause cannot stand alone. As you read it, your mind says ‘This is unfinished’. There has to be something else to make it into a sentence. That something else will necessarily include a finite verb form which gives the sentence its tense.

All sentences have a subject and a verb. The sentence “Jackie hit the ball” is indeed a sentence, so Jackie is the subject and hit is the verb. However, “Jackie, hitting the ball” is actually not a sentence, so it does not have a subject and a verb. In another response, someone said “Jackie, hitting the ball is dangerous.” Yes, this is a complete sentence, but “is” is the verb, because “hitting the ball” is the subject. Sure “hitting” is a verb, but in this instance, it is not used as a verb; I can’t remember what you call that (gerund, I think), but basically it functions as a noun.

As for what makes a verb have a tense, well, it depends primarily on when the action takes place. Simply, if the action has already taken place, the verb needs to be in “past tense” (I ate the cake yesterday). If the action is taking place right now, then the verb needs to be in “present tense” (I am eating the cake right now -OR- I eat the cake with milk.). If the action has not yet taken place, then the verb needs to be in “future tense” (Frank will eat the cake tomorrow.)

Of course, these are the very simplest of tenses; they do get much more complicated, and someone else has already discussed those.

Every verb has a tense. Always. In this case, if you saying:

“Jackie, hitting the ball is dangerous.”– ‘hitting’ is not the verb, it is the subject of your statement even though it technically is an action (but a physical action/not grammatically speaking).

SIMPLE PRESENT – is used to describe an action that is occurring in the present, at the moment of speaking. The simple present is used when the precise beginning or ending of a present action, event, or condition is unknown or is unimportant to the meaning of the sentence. In short, the child’s communication intent is about the action, and unconcerned about time of action aspects.

PRESENT PROGRESSIVE – While the simple present and the present progressive are sometimes used interchangeably, the present progressive emphasizes the on-going nature of an act at the time a person is speaking. Present progressive verbs are formed by using a present tense auxiliary verb and marking the main verb with an [ing] ending.

SIMPLE PAST – The simple past is used to describe an action that occurred in the past, sometime before the moment of speaking. The regular past tense verb is marked with the [ed] ending as in (walk – walked). There are seven different ways to mark the irregular past tense verb. The most common is to change the vowel as in (sing – sang)

PAST PROGRESSIVE – The past progressive tense is used to describe actions ongoing in the past. The on-going actions took place and were completed at some point well before the time of speaking. Past progressive verbs are formed by using a past tense auxiliary verb and marking the main verb with an [ing] ending.

SIMPLE FUTURE – The simple future is used to refer to actions that will take place after the act of speaking. The verb is unmarked, but requires a future tense auxiliary verb.

FUTURE PROGRESSIVE – The future progressive tense is used to describe actions ongoing in the future, after the act of speaking. Another way of expressing the meaning communicated by the future progressive verb tense is: an event that will be going on when something else happens. This form requires a future tense auxiliary verb, plus the main verb is marked with an [ing] ending.