High Quality Content by WIKIPEDIA articles! An important role in English grammar is played by determiners – words or phrases that precede a noun or noun phrase and serve to express its reference in the context. The most common of these are the definite and indefinite articles, the and a(n). Other deteminers in English include demonstratives such as this and that, possessives such as my and the boy`s, and quantifiers such as all, many and three.