Passers-by
The plural form of "passer-by" is "passers-by."
go-betweens
It is a plural, compound noun, from "cow + boys."
Some examples of compound words that are plural are: Passersby Court-martials Knights-errant
To form the plural of a compound noun, you generally add -s to the main noun in the compound if it's a regular plural form. For example, "book" in "bookstore" becomes "bookstores" in the plural. If the compound noun doesn't have a main noun, you can add -s to the end of the entire compound (e.g., "brother-in-law" becomes "brothers-in-law").
Compound subjects have at least two parts joined by or . . . nor, not only . . . but also, or and, as in snacks and fruit juice, and each part may be singular or plural. A plural subject has just one word as the simple subject, but that word is plural (like plates). Finally, a collective subject contains a simple subject representing a group (such as jury, which describes a group of twelve); the collective subject may be singular (jury) or plural (juries).
The plural form for the compound noun passer-by is passers-by.
Passerby is a compound word ending in by.
The plural form of "passerby" is "passersby."
The singular form is passerby; the plural for is passersby.
passers-by
passersby
The noun 'passerby' is the singular form. The plural form is passersby.
The possessive form for the noun passerby is passerby's.
The passerby did not stop to speak with him. She waved to the passerby.
The noun 'onlooker' is a single compound word, the plural is onlookers.
standbys
goings-on