§ 418.--_Apposition,_--_Cæsar, the Roman emperor, invades Britain._---Here the words _Roman emperor_ explain, or define, the word _Cæsar_; and the sentence, filled up, might stand, _Cæsar, that is, the Roman emperor_, &c. Again, the words _Roman emperor_ might be wholly ejected; or, if not ejected, they might be thrown into a parenthesis. The practical bearing of this fact is exhibited by changing the form of the sentence, and inserting the conjunction _and_. In this case, instead of one person, two are spoken of, and the verb _invades_ must be changed from the singular to the plural. Now the words _Roman emperor_ are said to be in apposition to _Cæsar_. They constitute, not an additional idea, but an explanation of the original one. They are, as it were, _laid alongside_ (_appositi_) of the word _Cæsar_. Cases of doubtful number, wherein two substantives precede a verb, and wherein it is uncertain whether the verb should be singular or plural, are decided by determining whether the substantives be in apposition or the contrary. No matter how many nouns there may be, as long as it can be shown that they are in apposition, the verb is in the singular number. § 419. _Collectiveness as opposed to plurality._--In sentences like _the meeting _was_ large_, _the multitude _pursue_ pleasure_, _meeting_ and _multitude_ are each collective nouns; that is, although they present the idea of a single object, that object consists of a plurality of individuals. Hence, _pursue_ is put in the plural number. To say, however, _the meeting were large_ would sound improper. The number of the verb that shall accompany a collective noun depends upon whether the idea of the multiplicity of individuals, or that of the unity of the aggregate, shall predominate. _Sand and salt and a mass of iron _is_ easier to bear than a man without understanding._--Let _sand and salt and a mass of iron_ be dealt with as a series of things the aggregate of which forms a mixture, and the expression is allowable. _The king and the lords and commons _forms_ an excellent frame of government._--Here the expression is doubtful. Substitute _with_ for the first _and_, and there is no doubt as to the propriety of the singular form _is_. § 420. _The reduction of complex forms to simple ones._--Take, for instance, the current illustration, viz., _the-king-of-Saxony's army_.--Here the assertion is, not that the army belongs to _Saxony_, but that it belongs to the _king of Saxony_; which words must, for the sake of taking a true view of the construction, be dealt with as a single word in the possessive case. Here two cases are dealt with as one; and a complex term is treated as a single word. The same reason applies to phrases like _the two king Williams_. If we say the _two kings William_, we must account for the phrase by apposition.