540. =Names of Orders= are given in the plural number, and are commonly formed by prolonging the name of a genus of the group taken as a representative of it. For example, the order of which the Buttercup or Crowfoot genus, _Ranunculus_, is the representative, takes from it the name of _Ranunculaceæ_; meaning _Plantæ Ranunculaceæ_ when written out in full, that is, Ranunculaceous Plants. Some old descriptive names of orders are kept up, such as _Cruciferæ_ for the order to which Cress and Mustard belong, from the cruciform appearance of their expanded corolla, and _Umbelliferæ_, from the flowers being in umbels. 541. =Names of Tribes=, also of suborders, subtribes, and the like, are plurals of the name of the typical genus, less prolonged, usually in _eæ_, _ineæ_, _ideæ_, etc. Thus the proper Buttercup tribe is _Ranunculeæ_, of the Clematis tribe, _Clematideæ_. While the Rose family is _Rosaceæ_, the special Rose tribe is _Roseæ_. 542. =Names of Classes, etc.= For these see the following synopsis of the actual classification adopted, p. 183. 543. So a plant is named in two words, the generic and the specific names, to which may be added a third, that of the variety, upon occasion. The generic name is peculiar: obviously it must not be used twice over in botany. The specific name must not be used twice over in the same genus, but is free for any other genus. A _Quercus alba_, or White Oak, is no hindrance to _Betula alba_, or White Birch; and so of other names. 544. =Characters and Descriptions.= Plants are _characterized_ by a terse statement, in botanical terms, of their peculiarities or distinguishing marks. The character of the order should include nothing which is common to the whole class it belongs to; that of the genus, nothing which is common to the order; that of the species nothing which is shared with all other species of the genus; and so of other divisions. _Descriptions_ may enter into complete details of the whole structure. 545. =Terminology=, also called _Glossology_, is nomenclature applied to organs or parts, and their forms or modifications. Each organ or special part has a substantive name of its own: shapes and other modifications of an organ or part are designated by adjective terms, or, when the forms are peculiar, substantive names are given to them. By the correct use of such botanical terms, and by proper subordination of the characters under the order, genus, species, etc., plants may be described and determined with much precision. The classical language of botany is Latin. While modern languages have their own names and terms, these usually lack the precision of the Latin or Latinized botanical terminology. Fortunately, this Latinized terminology has been largely adopted and incorporated into the English technical language of botany, thus securing precision. And these terms are largely the basis of specific names of plants.