The use of can to ask or grant permission has been common since the 19th century and is well established, although some feel may is more appropriate in formal contexts. May is relatively rare in negative constructions (mayn't is not common); cannot and can't are usual in such contexts. Can is usually used in standard spoken English when asking for permission. It is acceptable in most forms of written English, although in very formal writing, such as official instructions, may is often used instead: Persons under 14 unaccompanied by an adult may not enter. Learn how to use 'can' and 'can't' in this A1 Elementary grammar lesson. Clear rules, charts and exercises. Practise now! You use can to indicate that someone has the ability or opportunity to do something. Don't worry yourself about me, I can take care of myself. I can't give you details because I don't actually have any details. The United States will do whatever it can to help Greece. Canva is a free-to-use online graphic design tool. Use it to create social media posts, presentations, posters, videos, logos and more. CAN definition: to be able to; have the ability, power, or skill to. See examples of can used in a sentence. In this blog article we look at when and how you use the word can in English conversation. Get free tips from an expert teacher of English for Adults, at the British Council.