An apostrophe shows possession. An s (no apostrophe) added to the end of a word usually creates a plural.
If it is a singular possessive, like if one Phi Mu has a cute shirt, you would write, "Look at that Phi Mu's cute shirt." You wouldn't say that Phi Mus's shirt, because there's only ONE person that you're writing about.
If Delta Zeta has a cute bid day shirt and all their members are wearing it, you would write, "Look at the Delta Zetas' cute shirts." You add the s to the end of Delta Zeta to make it plural. Then you add the apostrophe to make it possessive.
How is it that you all got through high school and into college without understanding the difference between plural and possessive?
