The plural of a letter can be written using an apostrophe, which is usually not a valid way to form a plural. The plural spelling S's could also be a possessive, but Ss would probably be unclear. The phonetic version is esses, which is the plural of ess.
The plural of "S" is spelled "S's."
The plural is a normal S plural, races.
The plural is a normal S plural, associates.
The plural of "instrument" is spelled "instruments."
v i s i t o r s
The plural is bridges.
The plural of "instrument" is spelled "instruments."
The plural is a normal S plural, associates.
The plural is a normal S plural, races.
It is a normal S plural, worms.
The plural of hemisphere is the ordinary S form hemispheres.
The noun nominee has a normal S plural, nominees.
The word apostrophe has the normal S plural apostrophes.
The plural of "turkey" is "turkeys".
The noun daffodil has a normal S plural, daffodils.
To spell the plural of most names that end in S, you would add -es. Example: Jones-Joneses, Tess-Tesses
The word trampoline forms a normal S plural, trampolines.
v i s i t o r s