s sukienka lekki strój kobiecy, okrywający tułów i część nóg oraz ręce
dress noun UK US /dres/ A1 [C] a piece of clothing for women or girls that covers the top half of the body and hangs down over the legs: a long/short dress a wedding dress B2 [U] used, especially in combination, to refer to clothes of a particular type, especially those worn in particular situations: The king, in full ceremonial dress, presided over the ceremony.
as opposed to a skirt
skirt noun [C] UK /skɜːt/ US /skɝːt/ A1 a piece of clothing for women and girls that hangs from the waist and does not have legs:
so a skirt would be a spodnica
spódnica «część wierzchniego stroju kobiecego od pasa w dół»
So being a Scot I was aware of spodnica
and used męska spódnica szkocka
on many an opportunity
still it is nice to know
that there are differences
between a skirt and a dress
similarly spódnica and sukienkę
Then you have to be careful, because it's a false friend – „sukienka” is a lexicalised diminutive that means 'a dress' and it's non diminutive version(„suknia”) now means 'a formal dress'/'an evening gown'.
„Spódnica” is a polish word for 'skirt' and it's diminutive is „spódniczka”.
I suggest you should take a look at the book "False Friends of the Slavist", on wikibooks, it should make this course easier for you, I think. ;)