The word 'mucous' is an adjective, it has no plural form.
The noun 'mucus' is an uncountable (mass) noun as a word for a substance.
The word whims is a plural noun. The singular is whim.
The word beads is a plural noun. The singular is bead.
The word kindergarten is a singular noun. The plural form is kindergartens.
The word prefixes is a plural noun. The singular form is prefix.
The word apple is a singular noun. The plural would be apples.
The word team is singular; the plural form is teams.
These is plural, this is singular
Lance is singular. Lances is plural.
The word 'Phenomenon' is singular. The plural form is 'Phenomena'.
The word metastasis is singular, metastases is plural.
The word "ground" can be both singular and plural. Singular: "The ground is wet." Plural: "The grounds of the park are well-maintained."
Louse is singular. The plural form is lice.
No, the word "list" is singular. The plural form of "list" is "lists."
Verbs cannot be singular or plural. Has is after singular nouns.
It's singular. The plural is cafeterias.
Tool is singular. Tools is plural.
Caveman is singular. Cavemen is plural.