One or two words?

ALL READY/ ALREADY.


All ready means "completely ready".

i.e: "Are you all ready for the test?"



Already (adverb) means "before the present time" or "earlier than the time expected".

i.e:
I asked him to come to the cinema but he had already seen the film.
Are you buying Christmas cards already? It's only September!



ALL TOGETHER/ ALTOGETHER.

All together (adverb) means "together in a single group."

i.e: The waiter asked if we were all together.



Altogether (adverb) means "completely" or "in total ".

i.e: She wrote less and less often, and eventually she stopped altogether.

("To be in the altogether" is an old-fashioned term for being naked! Como dios lo trajo al mundo.)



ANY ONE/ ANYONE.

Any one means any single person or thing out of a group of people or things.

i.e: I can´t recommend any one of the books on this site.




Anyone means any person. It's always written as one word.

i.e: Did anyone see Big Brother yesterday?



APART/ A PART.

Apart (adverb) separated by distance or time.

i.e: They split up (cortar una relación) last summer, they´ve been apart for three months now.



A part (noun) a piece of something that forms the whole of something.

i.e: They made me feel like I was a part of the family.




EVERY DAY/ EVERYDAY.

Every day. In this expression, every is a determiner and day is a noun.
When you say every day you mean each day without exception.

i.e: You have been late for school every day this week.



Everyday (adjective).
When you say everyday you mean ordinary, unremarkable.

i.e: My culture pages offer an insight into the everyday life of Britain.