the grammar of the Tamil language, Tolkāppiyam, argued to have been written around 2,500 years ago, classifies Tamil words as peyar (பெயர்; noun), vinai (வினை; verb), idai (part of speech which modifies the relationships between verbs and nouns), and uri (word that further qualifies a noun or verb). Western tradition A century or two after the work of Yāska, the Greek scholar Plato wrote in his Cratylus dialog, "sentences are, I conceive, a combination of verbs [rhêma] and nouns [ónoma]". Aristotle added another class, "conjunction" [sýndesmos], which included not only the words known today as conjunctions, but also other parts (the interpretations differ; in one interpretation it is pronouns, prepositions, and the article). By the end of the 2nd century BCE, grammarians had expanded this classification scheme into eight categories, seen in the Art of Grammar, attributed to Dionysius Thrax: 'Name' (ónoma) translated as "Noun": a part of speech inflected for case, signifying a concrete or abstract entity. It includes various species like nouns, adjectives, proper nouns, appellatives, collectives, ordinals, numerals and more. Verb (rhêma): a part of speech without case inflection, but inflected for tense, person and number, signifying an activity or process performed or undergone Participle (metokhḗ): a part of speech sharing features of the verb and the noun Article (árthron): a declinable part of speech, taken to include the definite article, but also the basic relative pronoun Pronoun (antōnymíā): a part of speech substitutable for a noun and marked for a person Preposition (próthesis): a part of speech placed before other words in composition and in syntax Adverb (epírrhēma): a part of speech without inflection, in modification of or in addition to a verb, adjective, clause, sentence, or other adverb Conjunction (sýndesmos): a part of speech binding together the discourse and filling gaps in its interpretation It can be seen that these parts of speech are defined by morphological, syntactic and semantic criteria. The Latin grammarian Priscian (fl. 500 CE) modified the above eightfold system, excluding "article" (since the Latin language, unlike Greek, does not have articles) but adding "interjection". The Latin names for the parts of speech, from which the corresponding modern English terms derive, were nomen, verbum, participium, pronomen, praepositio, adverbium, conjunctio and interjectio. The category nomen included substantives (nomen substantivum, corresponding to what are today called nouns in English), adjectives (nomen adjectivum) and numerals (nomen numerale). This is reflected in the older English terminology