two. The elliptical dual is notable in the Vedic Sanskrit, according to Jamison, where a noun in the dual signals a paired opposition. Illustrations include dyāvā (literally, "the two heavens" for heaven-and-earth), mātarā (literally, "the two mothers" for mother-and-father). A verb may be singular, dual or plural, while the person recognized in the language are forms of "I", "you", "he/she/it", "we" and "they". There are three persons in Sanskrit: first, second and third. Sanskrit uses the 3×3 grid formed by the three numbers and the three persons parameters as the paradigm and the basic building block of its verbal system. Gender, mood The Sanskrit language incorporates three genders: feminine, masculine and neuter. All nouns have inherent gender. With some exceptions, personal pronouns have no gender. Exceptions include demonstrative and anaphoric pronouns. Derivation of a word is used to express the feminine. Two most common derivations come from feminine-forming suffixes, the -ā- (आ, Rādhā) and -ī- (ई, Rukmīnī). The masculine and neuter are much simpler, and the difference between them is primarily inflectional. Similar affixes for the feminine are found in many Indo-European languages, states Burrow, suggesting links of the Sanskrit to its PIE heritage. Pronouns in Sanskrit include the personal pronouns of the first and second persons, unmarked for gender, and a larger number of gender-distinguishing pronouns and adjectives. Examples of the former include ahám (first singular), vayám (first plural) and yūyám (second plural). The latter can be demonstrative, deictic or anaphoric. Both the Vedic and Classical Sanskrit share the sá/tám pronominal stem, and this is the closest element to a third person pronoun and an article in the Sanskrit language, states Jamison. Indicative, potential and imperative are the three mood forms in Sanskrit. Prosody, metre The Sanskrit language formally incorporates poetic metres. By the late Vedic era, this developed into a field of study; it was central to the composition of the Hindu literature, including the later Vedic texts. This study of Sanskrit prosody is called chandas, and is considered one of the six Vedangas, or limbs of Vedic studies. Sanskrit prosody includes linear and non-linear systems. The system started off with seven major metres, according to Annette Wilke and Oliver Moebus, called the "seven birds" or "seven mouths of Brihaspati", and each had its own rhythm, movements and aesthetics wherein a non-linear structure (aperiodicity) was mapped into a four verse polymorphic linear sequence. A syllable in Sanskrit is