These two words mean exactly the same. They can be used both as prepositions and conjunctions. Till is more common in an informal style. Note that in American English, the preferred informal spelling of till is ’til.
- I waited until 6 o’clock and then I went home. OR I waited till 6 o’clock and then I went home.
- I will wait till / until I hear from you.
The preposition to is sometimes used instead of till and until. This usually happens after from…
- I usually work from ten to six. (OR I usually work from ten until / till six.)
Until and till both show time. They cannot be used to talk about distance. Instead we use to, as far as or up to.
- We walked as far as the edge of the forest. (NOT We walked until the edge of the forest.)
To talk about quantity we can use up to.
This car can seat up to eight people. (NOT This car can seat until eight people.)
Tenses with until
After until we use present tenses to talk about the future.
- I will wait until she comes. (NOT I will wait until she will come.)
Not until / till can mean the same as not before.
- We won’t be seeing each other until / before Christmas.