No natural English speaker would say it is a classical dress. They might say it is a class dress, or the dress is a classic
Please fix this.
"Classy" is a word I hate, because it means so many things to so many different people. here, in this translation, classic is better, because as you say classic means something that has been around a long time. I was going to say traditional, but that's more rooted in customs and habits.
In French, in particular, classique means "standard, normal", I suspect it is similar in Portuguese, I must check.
"Classy" means "elegant, stylish", according to the dictionary...
"Classic/classical" both mean "typical", "serving as standard of excellence", "traditional", "historically memorable"
For this sentence I don't believe one is better than the other, because all can be accurately used to describe the dress. DL just needs to add a few synonyms :D
What would this refer to in Brazil?
-An old-fashioned "classical" dress (like a Victorian style dress or even a toga, lol)? -A basic "classic" wardrobe staple (like a little black dress)? -A stylish "classy" elegant dress (like a ball gown or fancy cocktail dress)?
This dress description is not something I hear often in English, so I'm wondering if it means something specific in Portuguese.
You mean this one I think: "O chapéu dela é clássico."
Here's another sentence with "clássico": "O dia começou como um clássico domingo."
When talking about clothing I think both classic and classical could work given the right context, when talking about Sunday (as in the second example), classical sounds very odd.
Sadly, probably yes, unless the "hat" was really headgear dating from ancient Greece or Rome. The same here; to be described as "classical" the dress should really come from, or be modelled on one from that period and though that could work, both sentences are better suited to "classic". See (particularly the usage note at the end):
Thankfully, because the same word is used for both "classic" and "classical", these niceties are of no concern in Portuguese.
'Classical' normal means in British English, that something behind in a particular period - either ancient Rome and Greece, or inspired by them. Classical music is another period - art music from 1600 to 1920, roughly.
'Classic' means typical / timeless / very good example.
So in British English classic and Classical mean very different things, particularly when applied to a dress. Classical dress means clothing inspired by ancient Greece and Rome. A women's dress which is not historical costume can only be 'classic'