plexus [Lat. ‘intertwined’]

Subcategory of number of nouns and verbs which usually serves to indicate the presence of more than one element, but which can also have an individualizing function with certain common nouns (rock: rocks) and collective nouns (people: peoples). There are

Sing and dance

Susan and Figaro

formed by adding -(e)s (cats, dogs, bosses); other types of plural formation include foreign suffixes (phenomenon: phenomena) and changes in the stem (mouse: mice). ( also mutation)

References

Greenberg, J. 1974. Numeral classifiers and substantial number: problems in the genesis of a linguistic type. PICL 11. 17-37.