Seeds called "beans" are often included among the crops called "pulses" (legumes), although the words are not always interchangeable (usage varies by plant variety and by region). Both terms, beans and pulses, are usually reserved for grain crops and thus exclude those legumes that have tiny seeds and are used exclusively for non-grain purposes (forage, hay, and silage), such as clover and alfalfa. The United Nations Food and Agriculture Organization defines "BEANS, DRY" (item code 176) as applicable only to species of Phaseolus. This is one of various examples of how narrower word senses enforced in trade regulations or botany often coexist in natural language with broader senses in culinary use and general use; other common examples are the narrow sense of the word nut and the broader sense of the word nut, and the fact that tomatoes are fruit, botanically speaking, but are often treated as vegetables in culinary and general usage. Relatedly, another detail of usage is that several species of plants that are sometimes called beans, including Vigna angularis (azuki bean), mungo (black gram), radiata (green gram), and aconitifolia (moth bean), were once classified as Phaseolus but later reclassified—but the taxonomic revision does not entirely stop the use of well-established senses in general usage.