It is sometimes desirable to refer to a noun in both its singular and plural form. The convention for doing so, for regular nouns that take the s-ending in plural, is to add the s and enclose it in parentheses.
Reserved time slots are now labeled “You have x machine(s) booked,” so that the user knows how many, and which, machines they have access to.
For irrregular nouns that do not take the s-ending in plural (like one man, two men), one usually must write out both forms combine by the word or.
The man or men who built this altar took care to orient it in a north-south direction.