Till is not a shortened form of until but is the older word; the un- of until adds the element 'up to, as far as'. The two words can both be used as prepositions (e.g. until/till tomorrow) or conjunctions (e.g. until/till we reach home) They are largely interchangeable, except that until is more usual at the beginning of a sentence and can sound somewhat more formal, especially in speech.

Read more: until-till-usage

• It is spelled 'till. An apostrophe is needed because it is part of a word- until, 'till.

• It is " 'til' ", it comes from the word "until", which only has 1 letter L . Yes, you DO need an apostrophe.

• It's both because 'til is shortened for "until" but if you look up till in the dictionary, you'll find that one definition is "up to the time of; until: to fight till death."

• It's both because 'til has come into common usage over the last hundred years or so, as a contraction of until. However, till is not derived from until. Till is the older word, in use for about 1,200 years, whereas until is a relatively recent word, maybe 800 years old.

• The older word is til.