Hi Lena, I would always 'until' in written English, unless I am writing slang dialogue for a character in a story. When speaking with friends, I would say both 'until' and 'till' interchangeably, but not intentionally. 'Till' is a more informal phrase that would be considered as slag. I hope my answer helps you, Tom

I think the advise here depends on the country. Till is actually fine to use in most contexts and is not an abbreviation like most people think. The words can actually be used interchangeably in most countries and it comes down more to personal preference. If you just stick with until though you'll be fine. That works everywhere and means exactly the same thing.

If you're speaking, you can use till and until interchangeably - even in formal (ie at work) or informal situations (ie with your friends). For writing, always use until.

I always use "until" in formal writing. "Till" is a bit slang if you write it.