 From the 16th century, following French practice, the apostrophe was used when a vowel letter was omitted either because of incidental elision ("I'm" for "I am") or because the letter no longer represented a sound ("lov'd" for "loved").English spelling retained many inflections that were not pronounced as syllables, notably verb endings ("-est, -eth, -es, -ed") and the noun ending "-es", which marked either plurals or possessives (also known as genitives; see Possessive apostrophe, below).So an apostrophe followed by "s" was often used to mark a plural, especially when the noun was a loan word (and especially a word ending in "a", as in "the two comma's").