The word determiner is unlikely to occur in older grammar books, but it is a useful term for some of the most common words in any language. Determiners come first in a noun phrase, before adjectivites and before numbers (which are also determiners). Unlike ordinary adjectives, determiners don´t describe nouns, but put nouns in context, to say whether they are assumed to be known or unknown, to say who they belong to, how many there are, whether they are here or over there.