Irridium said:
what's the plural of axis? Axii. Axises, Axis'?
The plural of "axis" is "axes". Words in "-is" take their plural in "-es" (thesis -> theses; basis -> bases) with "-ises" occasionally accepted (penis -> penises or penes, sorted in order of use/acceptance).
"-ii" is the plural of "-ius" (or rather, "-i" is the plural form of "-us", which I guess could lead to two Is in a row although I can't think of an example.). Ex: cactus -> cacti, fungus -> fungi. Note that some words in "-us" are still pluralized "-uses" (virus -> viruses) and some have many accepted plurals (octopus -> octopuses, octopodes or octopi, sorted in order of use/acceptance)
Apostrophes are never used to mark a plural, an apostrophe after a plural word ending in S marks a possessive (not that if the word is singular or doesn't end in S, you still us apostrophe+s as usual. For instance, "Ross's brush", "people's opinions". In the first example, note that it's also pronounced like "Rosses".)
Sometimes people use an apostrophe to mark a plural, but they do it before the S. In such cases, it's still correct not to use the apostrophe (the 8os, I have CDs) although using it is common so I guess it's also accepted?
To answer the OP's question, I use whichever controls are the default, inverted or not.