Locke wrote that the use of words "is to be sensible marks of ideas", though they are chosen "not by any natural connexion that there is between particular articulate sounds and certain ideas, for then there would be but one language amongst all men; but by a voluntary imposition, whereby such a word is made arbitrarily the mark of such an idea". Wittgenstein's thought transitioned from a word as representation of meaning to "the meaning of a word is its use in the language." Classes Each word belongs to a category, based on shared grammatical properties. Typically, a language's lexicon may be classified into several such groups of words. The total number of categories as well as their types are not universal and vary among languages. For example, English has a group of words called articles, such as the (the definite article) or a (the indefinite article), which mark definiteness or identifiability. This class is not present in Japanese, which depends on context to indicate this difference. On the other hand, Japanese has a class of words called particles which are used to mark noun phrases according to their grammatical function or thematic relation, which English marks using word order or prosody. It is not clear if any categories other than interjection are universal parts of human language. The basic bipartite division that is ubiquitous in natural languages is that of nouns vs verbs. However, in some Wakashan and Salish languages, all content words may be understood as verbal in nature. In Lushootseed, a Salish language, all words with 'noun-like' meanings can be used predicatively, where they function like verb. For example, the word sbiaw can be understood as '(is a) coyote' rather than simply 'coyote'. On the other hand, in Eskimo–Aleut languages all content words can be analyzed as nominal, with agentive nouns serving the role closest to verbs. Finally, in some Austronesian languages it is not clear whether the distinction is applicable and all words can be best described as interjections which can perform the roles of other categories. The current classification of words into classes is based on the work of Dionysius Thrax, who, in the 1st century BC, distinguished eight categories of Ancient Greek words: noun, verb, participle, article, pronoun, preposition, adverb, and conjunction. Later Latin authors, Apollonius Dyscolus and Priscian, applied his framework to their own language; since Latin has no articles, they replaced this