I found this, but more (with this what I put down here) about conjuctions you can find here: http://basic-croatian.blogspot.com/2009/06/35.html Rarely (almost never) we use "i" instead of "a" because that sounds strange. It's not standard. So, it's not convinient to interchange "i" and "a". Those two conjuctions ("i" and "a") are in different groups of conjuctions. Conjunction "i" (and) links two words, phrases, or sentences that are both on equal footing, in no opposition whatsoever, and used in a positive sense: Ivan i Ana rade. "Ivan and Ana are working". (two nouns) Ivan je žedan i gladan. "Ivan is thirsty and hungry". (two adjectives) Ivan je jeo i pio. "Ivan was eating and drinking". (two participles) Ivan jede i pije. "Ivan is eating and drinking". (two verbs) Uredi su u prizemlju i na katu. "Offices are on the ground floor and on the first floor". (two phrases) With conjunctions "a" and "ali" we can join only two sentences, or two phrases or verbs into another one. The conjunction "a" means just a contrast, and "ali" an opposition. In many cases, English translates "a" as "and": Ivan radi, a Ana spava. "Ivan is working, and Ana is sleeping." Ivan radi, ali samo do podneva. "Ivan is working, but only until noon." Ivan danas radi, ali sutra ne radi. "Ivan is working today, but tomorrow he's not working".