Croatian has basically two conjunctions that correspond to English and:
The conjunction i¨ is used when you want to join two words or two parts of sentences:
Ivan i Ana rade. Ivan and Ana are working. (nouns)
Ana je žedna i gladna. Ivan is thirsty and hungry. (two adjectives)
Sobe su u prizemlju i na katu. The rooms are on the ground floor and on the first floor. (two locations)
It's possible to join two normal-type sentences (that is, two verbs) that have the same subject:
Ana jede i pije. Ana is eating and drinking.
[Pijem čaj] i [čitam knjigu]. I'm drinking tea and reading a book.
Here we actually join two clauses (I have put square brackets around each of them in the last sentence).
It's also possible to join two subjective-experience-type sentences, if they have the same experiencer (in DL):
Hladno mi je i dosadno. I'm cold and bored.
However, if you want to join two sentences that have different subjects, you have to use the conjunction a¨:
Ana čita knjigu, a Goran spava. Ana is reading a book, and Goran is sleeping.
When an a¨ is used, a comma always separates two clauses.
Now there's a very interesting rule. If you have different subjects – and consequently use a¨ – the subjects must be emphasized. That is, you have to use them:
Ana čita knjigu, a ja spavam. Ana is reading a book, and I'm sleeping.
You cannot use the previous sentence with just a spavam!
The same works for experiencers: they must be emphasized, that is, stressed forms of pronouns must be used:
Ana se zabavlja, a meni je dosadno. Ana is having fun, and I'm bored.
Again, you cannot use the previous sentence with just a dosadno mi je!
The conjunction a¨ is also used if there's some opposition between two clauses, e.g.
Zabavljam se, a trebao bih učiti. I'm having fun, and I should study.
In such a case, when the subjects are the same in both clauses – as above – they are not emphasized.
As other words marked with ¨, words i¨ and a¨ don't count – second position words cannot be placed after them:
Ana je čitala knjigu, a ja sam² spavao. Ana was reading a book, and I was sleeping.
Gledam film i dosadno mi² je². I'm watching a movie, and I'm bored.
Another exception to the "rule of different subjects" is when the second clause is a consequence of the first, then the emphasis of the subject of first clause is not needed:
Pokucao sam i ona je otvorila vrata. I knocked and she opened the door.
The next conjunction – ili – is very similar to English or:
To je patka ili guska. That's a duck or a goose.
Unlike i¨ or a¨, ili is a word that counts, and all second-position words come right after it.
The conjunction ali corresponds to English but:
Hoću se tuširati, ali nema tople vode. I want to have a shower, but there's no hot water.
Again, when an ali is used, a comma always separates two clauses. The major difference in comparison to a¨ is that ali is a word that counts, and all second-position words come right after it.
There's a simple way to emphasize that all subjects/actions/objects/places/whatever are involved, like in English both... and.... In Croatian, simply an i¨ is placed before each emphasized item:
I Ivan i Ana rade. Both Ivan and Ana are working.
Sobe su i u prizemlju i na katu. The rooms are both on the ground floor and on the first floor.
However, if you want to make an emphasis in a sentence where the verb is negated, you should use negative conjunctions ni¨ instead, but the verb is still negated:
Ni Ivan ni Ana ne rade. Neither Ivan nor Ana are working.
Sobe nisu ni u prizemlju ni na katu. The rooms are neither on the ground floor nor on the first floor.
As you can see, this corresponds to English neither... nor..., but the major difference is that the verb is negated in Croatian sentences.
To emphasize that only one option is possible, you can use ili... ili..., corresponding to English either... or:
To je ili patka ili guska. That's either a duck or a goose.
(The rest is coming soon.)