What is the difference between chi'n vs chi or i'n vs i? Thank you.
I'n is a contraction of i yn. Sometimes you can contract them ("Dw i'n hoffi coffi"), and sometimes you cannot ("Dw i ddim yn hoffi coffi"). Chi vs chi'n is the same way. I'm not quite sure what 'yn' means, though.
'yn' is a linking word needed between the verb (dw i - I am) and the verb noun (hoffi - to like) to create 'I like' (literally, 'I am liking')
Mewn and yn both mean 'in'. Mewn is used when you are in an unspecified place (usually no 'the' following it) and yn is specific (a 'the' comes next!) For example - 'Dw i mewn swyddfa' (I am in an office) as opposed to 'Dw i yn y swyddfa' (I am in the office)