* Single quotation mark ('): This is the most common symbol that looks like an apostrophe. It is used to enclose words or phrases that are being quoted, to indicate possession, and in some cases, to denote contractions.
* Prime symbol (′): This symbol is often used in mathematics to denote feet or minutes.
* Acute accent (´): This symbol is used in some languages, like Spanish and French, to modify the pronunciation of vowels.
* Grave accent (`): This symbol is also used in some languages, like Italian and French, to modify the pronunciation of vowels.
If you're unsure which symbol is being used, it's best to look at the context in which it appears. For example, if you see the symbol next to a number, it's likely a prime symbol indicating feet or minutes. If you see it used to enclose a word or phrase, it's likely a single quotation mark.