"Your shirt is clean."
Translation:Ta chemise est propre.
Vos is used in a sentence like this:
'Vos hommes sont bons'
which is plural of:
'Votre homme est bon'.
See the difference? The equivalent for that if you're only saying it to one person (or you know them very well), then you say:
'Tes hommes sont bons'
'Ton homme est bon'.
Mon/ masculine singular, Ma/ feminine singular, Mes/ plural = my
Ton/ masculine singular, Ta/ feminine singular, Tes/ plural = your (informa)
Son/ masculine singular, Sa/ feminine singular, Ses/ plural = his/ her
All of the preceding forms are determined by the noun they are attached to not the subject of the sentence or phrase. Masculine singular forms go with masculine singular nouns etc. If you are talking about a woman who owns a male dog it is her dog = son chien because chien is masculine. If you are talking about a man who owns a female dog it is his dog = sa chienne because chienne is feminine.