What is the difference between Alexis' and Alexis's?

Answer 1

The difference is that only Alexis's is correct. The possessive singular of all English nouns, regardless of spelling, is formed by the addition of -'s. Singular possessives sound as if they were plurals. In the case of singular nouns already ending in -s, the possessive gains a syllable just as the plural does (compare fox / fox's: fox / foxes).

Some believe and even teach (!) that the plural form is correct for singulars, but they are wrong. The proof is in the pronunciation. Since the apostrophe has no sound, Alexis' has the same number of syllables that Alexis has, and therefor it cannot be the correct possessive.

Answer 2

Both "Alexis'" and "Alexis's" are possessive forms of the name Alexis. "Alexis'" is used when the name ends in an "s" sound, while "Alexis's" is used for most other cases. So, for example, you would write "Alexis' car" but "Alexis's book."