(grammar) A noun (either in certain of its senses or in all its senses) that does not generally have a singular form.

plural of plurale tantum

plural of singulare tantum

(grammar) A noun (in any specific sense) that has no plural form and is only used with singular verbs. Frequently for mass nouns.

plural of duale tantum

(grammar) A noun (or specific sense of a noun) that can only occur in the dual, and which lacks forms for singular, plural, and any other number.