Learning English can sometimes be a bit of a challenge. For plenty of English learning students, it can be easy to confuse the word can with could.

If you have a bit of a hard time knowing when to use which, then continue reading to find out what the difference is between using can and could and when to use which.

When do you use the word can?

Can is a model auxiliary verb, meaning it helps other verbs by indicating possibility, and ability. Can is also used to ask or give permission. 

Some example sentences that use the word can to indicate ability are:

“I can speak fluent English.”

“I can swim quite well.”

“I am not working tomorrow so I can help you move.”

Can is also used when want to talk about things that can possibly happen. 

Some example sentences that use can to show possibility are:

“Furniture prices can be very high this time of year.”

“Climate change can cause extreme heat or extreme cold.”

“I am very busy, but if I have the night off, I can attend your party.”

When we want to ask or give permission, we use the word can:

“Can I please have a ride?”

“Yes, you can join my grammar class.”

“Can you please teach me some new vocabulary words?”

The word can is known for being an irregular verb. An irregular verb is a verb that does not stick to normal tense patterns. Irregular verbs are distinctive because they are known for having their own past participles (when you add -ed or -d to the end of a verb, for example, saved, and liked), and their own tenses.

When do you use the word could?

Could is the simple past tense of the word can. 

This form can also be used to show ability:

“A few years ago, I could also do that.”

“If I had the right equipment then I could join.”

“I could speak English very well, but I have forgotten some grammar rules.”

It is important to know that when you use could, it is not used to give permission, but rather to ask for it.

For example:

“Could I please have some fries?”

“Could I possibly leave earlier today?”

“It is very hot in here. Could you please open a window?”

When using could to indicate possibility, we normally use the present perfect tense:

“His driving could cause an accident.”

“My English teacher said it could rain today.”

“If I had more time then I could help out more.”

Could can be used to talk about, the past, the present, and the future. When it is used to refer to the past, it is normally paired with have, which is also an auxiliary verb:

“If you studied more then you could have achieved better English marks.”

“You could have saved money by buying the cheaper pair of shoes.”

“He could have borrowed an English language book, but he decided to rather buy it.”