determiner Every individual or anything of the given class, with no exceptions (the noun or noun phrase denoting the class must be plural or uncountable).
All contestants must register for the footrace: we've arranged numbers for them all.
determiner Throughout the whole of (a stated period of time; generally used with units of a day or longer).
The store is open all day and all night.
determiner Only; alone; nothing but.
He's all talk; he never puts his ideas into practice.