This is, methinks, the 20th time I've translated this sentence. What's this obsession with square bottles, Duolingo?
Isn't the bottle cubic? Cubes are 3-dimensional; squares are 2-dimensional. 3-D items aren't "square" in English. Are they square in Portuguese???
No, they are not. This is just what is common to say, just like in English it is common to call the sun a "circle" in the sky, even though it is a sphere. People are naturally in their speech, which makes words like «cubo»/«cúbico» and "spherical" sound unnatural for normal, everyday speech.
First time answering, but isnt this the section for "places"? How is this related?
Maybe they don't want us to mix up adj. quardada (square) with n. praça (square).
When you go to a restaurant? Duolingo does not always keep to the topic and often brings back sentences from previous skills, although I do not ever remember encountering this one before.
Two definitions are given for quadrada: square and square (sing fem). So could I also say quadrado (masc)? Is that a word? And does this just mean that in most cases you would use the word with an 'a' at the end?
There is the shape itself, a noun: «o quadrado» (always masculine). When describing objects, «quadrado» loses the article and must match the gender of the described object: «uma garrafa quadrada» or «um rosto quadrado».
Because it would mean "a garrafa é enquadrada", when we want to say "a garrafa é quadrada".
Isn't praça and quarada square? How would I use each one separately & differently in a sentence?
Use «quadrado» for the shape that you draw. Use «quadrado(s)»/«quadrada(s)» as adjectives to describe things, as in this sentence. Use «praça» only for a "town square." FYI, «a quadra» means "court" as in those in which you play tennis or basketball.