Can vs Could
Can and could are modals. These are auxiliary words that are used with a main verb, whose uses in grammar are often confused with. Can is in the present tense while could is in the past tense. However, these two are used in many ways.
Can in the present tense is used to state a fact and declare ability. When used in the sentence, the word can state the fact that someone has the ability, or he knows how to do a thing and that he has the skill to do it. Can is also used to express possibility and things that can be done potentially.
Could is used as a past tense of can to state an ability in the past or the things one was able to do in past but not anymore. In addition to that, could express possibility as well but the time is just stated in the past. The word could is also used to state condition as is the sentence, “If I had money, I could buy you a car”.
Difference between Can and Could
Both can and could are used in imperative expressions usually in question form. They are used to make requests or permissions, but the use of could suggests a more polite mood. Example of this usage is this sentence, “Can I leave now? Could you get me a glass of water?” Moreover, the use of could suggests a level of doubt and uncertainty. This means that when the word could is used in the sentence the meaning may suggest that the information being expressed is maybe true or not. Can may express that a person is able to do, while could about 50% possibility that it will be done.
Can and could are sometimes very confusing, however, given the pointers above, you can get passed the confusion because simply you can.
• Can is used to state a fact, ability, potential, and possibility.
• Could is used to state a past ability, condition, and possibility.
• Can and could are used to make a permissions, requests or commands
• Could suggests a polite manner when making a request and it suggests a level of doubt or certainty