Can or could

AnonymousAre both possible

Yes.

Anonymousbut the use of can is more definitive?

No, it is more encouraging.

Thank you. S. Encouraging here means the possibility of happening is higher than 'could', may be?

AnonymousEncouraging here means the possibility of happening is higher than 'could',

No. If I had a child who was very worried that she might not do well, I would encourage her saying "You can do it." It has no implication of level of possibility.

"Could" would naturally be used with an "if" clause:

You could do it, if you didn't watch TV thi

Thanks. Can 'can' be used in your if clause example, or does the sentence have to be altered slightly, into the present form?

Also, when using could in the if clause, does the tenses used have to be in the past form, or can it be used in the present, eg:

You could do it if you don't watch TV this evening, and studied for the test instead.

What I am saying is do the tense

AnonymousThanks. Can 'can' be used in your if clause example, or does the sentence have to be altered slightly, into the present form?

Yes.
You can pass the test if you study hard tonight. (Here it is almost a guarantee that you will pass the test if you fulfill the condition.)

AnonymousAlso, when using could in the if clause, does

So the conditional form when using 'could' has to be in the past, just as in your example?

I was wondering if the same original sentence can be used with the word 'can' instead of 'could':
You can do it if you don't watch TV this evening, and studied for the test instead...... would that be correct?

Do the tenses have to match in the if clause, ...can with don't; could with d

AnonymousSo the conditional form when using 'could' has to be in the past, just as in your example?

Yes. It is a past form, but it is not past time. This form is called the present subjunctive. The subjunctive is used in second conditional sentences.
Here is a good resource:

I would not call 'could' a present subjunctive form. It can, in different contexts, be used in past-, present, and future-time situations but, if one accepts that modals have tensed forms, then 'could' is a past-tense form.

Sorry that I was unclear. The past form verbs in the if-clause are present subjunctive, not the modal (could/would) form in the main clause.

You could pass (modal, present) the test if you studied (subjunctive present) hard.

AlpheccaStarsSorry that I was unclear. The past form verbs in the if-clause are present subjunctive, not the modal (could/would) form in the main clause.You could pass (modal, present) the test if you studied (subjunctive present) hard.

Sorry, but I don't agree. 'Study' (all persons) is present subjunctive; 'studied' is past subjunctive.

It is imp