Possessive pronouns vs contractions

Being a native English speaker, I do not remember much of formal grammar. I simply go with what "sounds" right, which is how I judge whether or not I am being grammatically correct.

That being said, for some reason, I have been having issues with contractions and possessive pronouns recently. For instance, I seem to have forgotten the distinction between its vs it's. OK. that is easy enough- "its" represents a possessive pronoun, whereas "it's" represents a contraction for, say, it has or it is.

Fair enough. However, now let us take the example of Susan. To indicate that something belongs to Susan, we would say "Susan's", not "Susans".

My question then is- is there a rule/contradiction here? Why is it that its represents the possessive for it, but an apostrophe for Susan? Put differently, why is possession and well as contraction (say Susan has done this- Susan's done this) both expressed with an apostrophe?

Many thanks

Solution 1:

Here are some guidelines you can use to try to rememember them, as well as a possible rationale:

• Contractions always have an apostrophe where the letters are elided. So the contraction for "it is" is "it's".
• Nouns have "-s" appended for both pluralization and possession. The apostrophe is only used for possession, and distinguishes which is intended.
• Pronouns do not use "s" for pluralization -- they're irregular words that have a completely different form for the plurals. So they don't need to distinguish between plural and possessive use of "-s".
• Other possessive pronouns don't use an apostrophe -- "its" is formed similarly to "his", "hers", and "theirs".