Originally, all dialects distinguished singular, dual and plural numbers, but some of the more innovative dialects, such as those of Querétaro and of the Mezquital area, distinguish only singular and plural numbers, sometimes using the previous dual forms as a paucal number. The Ixtenco dialect distinguishes singular, plural, and mass plural numbers. The personal prefixes distinguish four persons, making for a total of eleven categories of grammatical person in most dialects. The grammatical number of nouns is indicated by the use of articles; the nouns themselves are unmarked for number.