The grammar determiner-p.grm handles determiner phrases which occur near the beginnings of noun phrases.  Examples are "the", "both those", "almost all my", "nearly every".  They are used in npcomponent.grm..  Semantically, many determiners can designate specific instances of things in the context, as chosen from the class of objects described by the noun(s) and descriptive adjectives in a noun phrase.

The node (an 1) in the determiner-p.grm module deserves special mention.  It is an initial node that is shown as ending a phrase of type "a".  Of course, "a" is not a phrase type, but rather the indefinite article.  So the node (an 1) just indicates that the article "an" is syntactically and semantically identical to "a".  (The difference between "an" and "a" is strictly morphological and phonotactic:  That is, they are just phonetic variants of the same indefinite article, the choice depending on whether or not the word following the article begins with one of certain vowel sounds or a consonant sound: "an apple/eagle/hour/igloo/owl/usher" versus "a banana/car/dog/house/man/unicorn/woman/year".  Notice that the initial "y" and "w" sounds in "unicorn", "woman", and "year" are not among the vowel sounds that are preceded by "an", and that words beginning with "h" are preceded by "an" if the "h" is un-aspirated as in "hour".)