Also we used to have three S's, three GLYPHS for the character or letter S:
S, ſ, s
The middle glyph is called "long s". Our lower case "s" was used only at the end of words originally.
The same thing is going on with the letter Sigma in Greek.
Σ, σ, ς
Arabic does this to the extreme, most of the letters in the Arabic alphabet have 4 glyphs; isolated, initial, medial and final.
https://en.wikipedia.org/wiki/Long_s
https://en.wikipedia.org/wiki/Sigma
https://en.wikipedia.org/wiki/Arabic_alphabet#Letter_forms