ut_, _series_. Care must be
taken in the use of these nouns, as in some cases their appearance is
misleading, e. g., _mathematics_, _physics_, and the like are singular
nouns having no plural, but owing to their form they are often mistaken
for plurals.

Compound nouns, that is to say, nouns formed by the combination of two
or three words which jointly express a single idea, generally change the
principal word in the forming of the plural, _hangers-on_, _ink
rollers_, but in a few cases both words change, for example,
_men-servants_. These forms must be learned by observation and practice.
It is very important, however, that they be thoroughly learned and
correctly used. Do not make such mistakes as _brother-in-laws_,
_man-servants_.

Perhaps the most important use of number is in the relation between the
noun and the verb. The verb as well as the noun has number forms and the
number of the noun used as subject should always agree with that of the
verb with which it is connected. Such expressions as "pigs is pigs,"
"how be you?" and the like, are among the most marked evidences of
ignorance to be found in common speech. When this paragraph was
originally written a group of high school boys were playing football
under the writer's window. Scraps of their talk forced themselves upon
his attention. Almost invariably such expressions as "you was," "they
was," "he don't," "it aint," and the like took the place of the
corresponding correct forms of speech.

Collective nouns, that is the nouns which indicate a considerable number
of units considered as a whole, such as _herd_, _crowd_, _congress_,
present some difficulties because the idea of the individuals in the
collection interferes with the idea of the collection itself. The
collective nouns call for the singular form of the verb except where the
thought applies to the individual parts of the collection rather than to
the collection as a whole, for instance, we say,

The crowd looks large.

but we say,

The crowd look happy.

because in one case we are thinking of the crowd and in the other of the
persons who compose the crowd. So in speaking of a committee, we may say

The Committee thinks that a certain thing should be done.

or that

The Committee think that a certain thing should be done.

The first phrase would indicate that the committee had considered and
acted on the subject and the statement represented a formal decision.
The se