this symbol ( ' ) is an apostrophe yes? When exactly do you use it? So far, I know it is used to "merge" two words like "isn't" and "we'll", but I'm not sure when it goes at the end of a word, like "Her sister's cat" or "her sisters' cat" or "her sisters' happy?" help
take for example the fine hijos de su madre from la real academia de españa, they justify their employment by adding a single moronic rule to the language every year