section_path: Structure/Grammar/Word classes
section_name: Word classes
paragraph_text: Word classes
  
  Languages organize their parts of speech into classes according to their functions and positions relative to other parts. All languages, for instance, make a basic distinction between a group of words that prototypically denotes things and concepts and a group of words that prototypically denotes actions and events. The first group, which includes English words such as "dog" and "song", are usually called nouns. The second, which includes "think" and "sing", are called verbs. Another common category is the adjective: words that describe properties or qualities of nouns, such as "red" or "big". Word classes can be "open" if new words can continuously be added to the class, or relatively "closed" if there is a fixed number of words in a class. In English, the class of pronouns is closed, whereas the class of adjectives is open, since an infinite number of adjectives can be constructed from verbs (e.g. "saddened") or nouns (e.g. with the -like suffix, as in "noun-like"). In other languages such as Korean, the situation is the opposite, and new pronouns can be constructed, whereas the number of adjectives is fixed.
  
  Word classes also carry out differing functions in grammar. Prototypically, verbs are used to construct predicates, while nouns are used as arguments of predicates. In a sentence such as "Sally runs", the predicate is "runs", because it is the word that predicates a specific state about its argument "Sally". Some verbs such as "curse" can take two arguments, e.g. "Sally cursed John". A predicate that can only take a single argument is called intransitive, while a predicate that can take two arguments is called transitive.
  
  Many other word classes exist in different languages, such as conjunctions like "and" that serve to join two sentences, articles that introduce a noun, interjections such as "wow!", or ideophones like "splash" that mimic the sound of some event. Some languages have positionals that describe the spatial position of an event or entity. Many languages have classifiers that identify countable nouns as belonging to a particular type or having a particular shape. For instance, in Japanese, the general noun classifier for humans is nin (人), and it is used for counting humans, whatever they are called:
  
  For trees, it would be: