Questions & Answers about Nie jestem pewien, czy mamy dobry żagiel.
Why is it pewien here instead of the standard adjective pewny?
Pewien is a special short-form adjective. In Polish, a few adjectives like pewny (sure), ciekawy (curious), and gotowy (ready) have these short forms (pewien, ciekaw, gotów). They are used exclusively as predicates, meaning they come after a verb like to be (here, jestem). You could also say Nie jestem pewny, but pewien is very common and natural in this exact phrase.
If a woman is speaking, does she also use pewien?
English uses 'if' here. Could I use jeśli or jeżeli instead of czy?
No, you must use czy. English uses 'if' for both conditions (If it rains...) and indirect questions (I am not sure if...). Polish strictly separates them. Because you are expressing uncertainty about a yes/no question (Do we have a good sail or not?), you must use czy. You only use jeśli or jeżeli for conditional statements.
Why does dobry żagiel look like it is in the nominative case when it is the object of mamy (we have)?