Are clothing items always singular when worn by multiple people? Are there other things that stay singular like this?
I think Hungarian only uses plural, when it's not redundant, so when no other parts of the sentence shows that there are more than one things. (I don't know if there are any cases when this is not true...)
Here are some examples where you use singular in Hungarian and plural in English:
A gyerekek könyvet olvasnak. = The children are reading books. (This is similar to the sentence above.)
Az eladó almát árul. = The shop assistant sells apples. (It's obvious that it's not only one apple.)
három kismalac = three little pigs (no plural after numbers)
sok autó = many cars
néhány autó = a few cars
Nadrágot hordok. = I am wearing pants.
Koszos a cipőm. = My shoes are dirty.
These "pair of..." things are singular in Hungarian: scissors = olló, glasses = szemüveg etc. Similarly:
Kék a szemem. = My eyes are blue.
I don't know what are the general rules, I just thought of some examples. I hope someone can explain it better.
I was taught that things that naturally come in pairs are treated as singular in Hungarian, such as eyes and hands. Someone who in English is one-eyed would be half-eyed (félszemű) in Hungarian.
So, am i correct that this sentence implies that there's a group of young men and every (or most) of them are wearing a shirt whereas if it would say "A fiatal férfiak ingekben vannak" that it would imply that there's a group of men and every (or most) of them are wearing multiple layers of shirts?
How do I say "I have a dirty shoe" referring one shoe (the other one needn't get washed)?
Az egyik cipőm koszos. = One of my shoes are dirty. ("one of my shoe is")
Van egy fél pár koszos cipőm. = I have half a pair of dirty shoes.
How to know when to use the suffix -n-on-en-ön and the suffix -ban-ben ?
Because in most of those sentences, it is the first option ("Egy piros ing van a kanadai férfin.") and in some others, like here, it is -ban-ben.
-n/-on/-en/-ön means "on" and -ban/-ben means "in".
Here are some examples:
A férfiak ingben vannak. = The men are in shirts. (The men are wearing shirts.)
A férfiakon ing van. = There are shirts on the men. (The men are wearing shirts.)
These two sentences mean the same.
A férfiak ingen vannak. = The men are on shirts. (The men are sitting/standing on shirts.)
A férfiakban ing van. = There are shirts in the men. (The men have eaten shirts.)
So, if we use the alternate option CORRECTLY and get marked off this should be reported to DuoLingo? Because I am experiencing this same problem. On a previous sentence "a gyereken is pulover van" I answered "a gyerek is puloverben van" and was marked incorrect.