Classifiers can be considered similar to genders or noun classes, in that a language which uses classifiers normally has a number of different ones, used with different sets of nouns. These sets depend largely on properties of the things that the nouns denote (for example, a particular classifier may be used for long thin objects, another for flat objects, another for people, another for abstracts, etc.), although sometimes a noun is associated with a particular classifier more by convention than for any obvious reason. However it is also possible for a given noun to be usable with any of several classifiers; for example, the Mandarin Chinese classifier () is frequently used as an alternative to various more specific classifiers.