Mambo rafiki! Please try thinking of the possesives, wako and yako, as two-dimension compound possesives. Then, I try to think like this:
w / y (possessive prefix) + ako (possessive stem)
1) the first would be the object dimension, then w corresponds to the singular objects, and y corresponds to the plural objects.
2) the second would be the people dimension, where ako corresponds to singular second person, and enu corresponds to plural second person.
Now, you can easily get the combinations:
For the singular second person, your umbrella would be mwavuli wako, and your umbrellas would be miavuli yako.
For the plural second person, your umbrella (for example, if you want to ask a couple with only one umbrella) would be mwavuli wenu, and your umbrellas would be miavuli yenu.
So, for this exercise, the two acceptable responses would be: miavuli yako and miavuli yenu.
Please remember that you see these possesives all the time as bidimensional words, in this case: w/y (object dimension), and -ako/-enu (people dimension), and you can try this with the other class nouns with all the possesives adjectives to get easily all the combinations.
When using nouns for people, the difference will be that the prefix used is only w. Then:
Your (sing.) sister = dada wako (with animate singular prefix w + singular second person stem -ako)
Your (pl.) sister = dada wenu (with animate singular prefix w + plural second person stem -enu)
Your (sing.) brothers and sisters = kaka na dada wako / when talking to one person, with animate plural prefix w
Your (pl.) brothers and sisters = kaka na dada wenu / when talking to more people, with animate plural prefix w
I hope it helps! :)
Here, other grammar notes:
In Swahili, possessives are formed by combining a possessive stem with the appropriate possessive prefix for the noun class of the possessed noun. Each personal pronoun has its own possessive stem:
First person singular: –angu (my)
Second person singular: –ako (your)
Third person singular: –ake (his/hers)*
First person plural: -etu (our)
Second person plural: -enu (y’alls)
Third person plural: -ao (their)* *
* All singular nouns use the 3rd person singular possessive stem
* * All plural nouns use the 3rd person plural possessive stem
SWAHILI: UNIT 9 – ASSOCIATIVES, POSSESSIVES, AND OTHER MODIFIERS