Some nouns—especially those ending in -s —although plural in form, are singular in number and in meaning: news, measles, mumps, calculus, rickets, billiards, molasses, dizziness, and other –ness ending nouns. These nouns require singular verb forms.

Are mumps plural?

The plural form of mumps is also mumps.

Is the word measles singular or plural?

The noun measles is plural only. The plural form of measles is also measles (obsolete).