Mumps is plural. But it is both singular and plural is construction.
Yes, the noun 'mumps' is a plural, uncountable noun, a word for an infectious disease.
The word team is singular; the plural form is teams.
These is plural, this is singular
The word metastasis is singular, metastases is plural.
The word "louse" is singular. The plural form is "lice."
No, the word "list" is singular. The plural form of "list" is "lists."
Caveman is singular. Cavemen is plural.
Verbs cannot be singular or plural. Has is after singular nouns.
It's singular. The plural is cafeterias.
Tool is singular. Tools is plural.
Singular Plural is caterpillars
Both singular and plural.