both are "your" but ty is one person (single you) so twój is belonging to the one person wy is plural you - more than one person - and wasz is belonging to wy
I'm from florida (so I'm not speaking for all americans) and I'm sure its not 'proper english' but it makes so much more sense to use "yall" or "y'all" when you mean to address multiple people
I'm still sticking with "y'all". If 'can not' becomes can't and will not becomes won't... why can't 'you all' become y'all :) Really I'm sticking with it because that is what I was raised saying, not because I think it is right =P
It looks like coming back to the roots... oiriginally English had thou, thine for 2nd person singular and you, your for plural. Then thou and thine went out of use and now it looks like you is shifting to singular and there is a need to introduce a new plural form. Interesting.
Twój = your / yours (2nd person singular) Wasz = your / yours (2nd person plural)
Twój = Nominative / masculine (used for 2nd person singular with a singular noun) Wasz = Nominative / masculine (used for 2nd person plural with a singular noun)
e.g.
This is your house. = To jest Twój dom. (you are speaking to Susie only) This is your house. = To jest Wasz dom. (you are speaking to Susie and Mark)
This house is yours. = Ten dom jest Twój. (you are speaking to Susie only) This house is yours. = Ten dom jest Wasz. (you are speaking to Susie and Mark)
Let`s remember that if we want to show respect, e.g, towards a person older and wiser than us, or simply a stranger, we shouldn`t say twój/was coz it suggests familiarity like with a friend or relative. Then one needs to use Pana/Pani - Mister`s/ Sir`s and Miss`/Madam`s.
In direct translation: Is this Mister`s book? instead of your book.:):):)