"Small and big ships sail on the deep seas."
Translation:A mély tengereken kis és nagy hajók úsznak.
Yes (?), 'uszni' is what Duo wants, but it's very poor.
'Sailing' works in English, b/c it has become the common reference from the days of the 'tall ships' - before engines.
'Vitorlazik' does not work in Hungarian, b/c it has remained to mean only wind-driven sails (although it also means 'floating'). Duo had to find an alternate translation. I suggested 'navigalni' (to navigate)
We use 'kis' when you want to say something like: ' Can I have a little salt?' or 'here is the little girl' (kaphatok egy kis sót?, itt a kislány) And we use kicsi when we want to say 'the girl is small', or 'my shoe is too small' (a lány kicsi, a cipőm túl kicsi) So 'kicsi' is something like small, and 'kis' is like little, but sometimes we mix it up For example: I need a little salt can mean that 'Kell nekem egy kis só' (it is better I think) but it can also mean that 'kell nekem egy kicsi só' (It is just a little bit weird but that's not a big deal). But sometimes we just can't mix them up 'cause it would be very weird, like "my shoe is too little"-"a cipőm túl kis". Do you see? It sounds weird.
I think my comment was ambiguous or I messed up the English word order. I meant that big and small ships sail on the deep seas and not somewhere else. It might help to get familiar with the parts of the sentence called topic and focus.
The phrase that starts the sentence (in yours: "kis és nagy hajók") is the topic. This is what you will form a statement about in the rest of the sentence.
The phrase preceding the conjugated verb (in your sentence: "a mély tengereken") is the focus. The focus is the element that excludes every other element of the same cathegory; in this case any place other than the deep seas is excluded.
This is not valid for all possible sentences, since it's not obligatory to include a topic and/or a focus, but it can be helpful when you're experimenting with word order and how it changes the meaning.