What words are plural without using

It seems like you're asking for words that are plural *without* using an "s" at the end. Here are some examples:

Irregular Plurals:

* Children (singular: child)

* Women (singular: woman)

* Men (singular: man)

* Feet (singular: foot)

* Teeth (singular: tooth)

* Mice (singular: mouse)

* Geese (singular: goose)

* Oxen (singular: ox)

* People (singular: person)

Words That Don't Change in Plural Form:

* Sheep (singular and plural)

* Fish (singular and plural, although "fishes" can refer to different species)

* Series (singular and plural)

* Species (singular and plural)

Compound Nouns with Plural Forms:

* Two-thirds

* Brothers-in-law

* Mothers-in-law

Words That Form Plurals Using Other Methods:

* Data (singular and plural)

* Criteria (singular: criterion)

* Phenomena (singular: phenomenon)

* Alumni (singular: alumnus/alumna)

Let me know if you'd like to explore other categories or have any more questions!