Okay, I checked about a dozen dictionaries; using an apostrophe was the most popular. They all listed the apostrophe option (a's, A's), most also listed adding the lone
s (as, As), and those were the only two options I found. I like using something to signal that the symbol is being used to refer to itself and was just reminded that angle brackets, < >, are commonly used to denote graphemes. (A grapheme is defined as either

1) an atomic unit of a writing system, e.g. a letter or punctuation mark, not necessarily representing a phoneme, or 2) a unit of a writing system, not necessarily atomic, that represents a phoneme. So since, in English, <ea, ee, ei, ey, i, ie, y> all represent the phoneme /i/, the vowel sound in
sheesh, they are all graphemes according to (2) but only the atomic <i, y> are graphemes according to (1). And since <!> is atomic in English but does not represent any English phonemes, it is a grapheme according to (1) but not (2). Again,

linguists can't manage to agree on definitions, like,
ever. Logicians have the same problem, only worse. You'd think they, of all people, would know better or try harder. Oy. It just really annoys me. Anywho...).
Personally, out of
ss
ss 's's "s"s <s>s
s's
s's 's''s "s"'s <s>'s
s's or <s>'s would be my first choices, depending on the context. I think ss,
ss, and s's are too ambiguous and 's''s and "s"'s are eyesores. But I probably think about these things too much.
On that note, my dictionary search turned up more
s uses. Yay.
-s is also used to form adverbs, as in
unawares, and
-'s also results from a contraction of
has, does, and
us, as in
What's been happening?, What's he want?, and
Let's go before we fall alseep. Captivated?
