There are three areas in Croatian – memory, expectations and fears – which are a bit different than in English. Each has a twist.
First, these verb pairs are used to express remembering and forgetting:
pamtiti ~~ za- (+ A/CC) memorize, remember
sjećati se² ~~ sjetiti se² (+ G/INF/CC) remember, recall
zaboravljati ~ zaboraviti (+ A/INF/CC) forget
The twist is that Croatian distinguishes storing into memory (zapamtiti) and retrieving something from memory (sjetiti se²) by means of two perfective verbs (as you can see from the double tildes, they are not ordinary perf. verbs, but it's not important for the moment). However, the two impf. verbs – pamtiti and sjećati se² – largely overlap in meaning; the latter verb is much more common in speech. In the meantime, English uses usually just remember:
Zapamtio sam gdje je auto. I remembered where the car is. (and now I know it)
Sjećam se gdje je auto. I recall where the car is. (I can get it from my memory)
The perf. verb sjetiti se² in past tense is often used to express that you have recalled something just now (and previously you couldn’t):
Sjetila sam se gdje je auto. I remember now where the car is. (female speaking)
It's also very common to use this verb when you remembered (or didn't) to do something (expressed in inf), so you did it (or didn't):
Jesi li se sjetio zatvoriti prozor? Did you remember to close the window?
If you didn't remember at some moment, you can also use the verb zaboraviti perf. forget, it's not necessarily permanent loss of memory:
Nisam se sjetio zatvoriti prozor. I didn't remember to close the window.
Zaboravio sam zatvoriti prozor. I forgot to close the window.
However, to memorize that you have to do something, you cannot use just inf – a content clause must be used:
Zapamtio sam [da moram zatvoriti prozor]. I ‘memorized’ I have to close the window. (i.e. I know it, I'll do it, you don't have to remind me)
The basic verb to express fear in Croatian is:
bojati (boji) se² (+ G/INF/clause)
Ana se boji zmija. Ana is afraid of snakes.
Another way is using the noun strah + the verb biti (je² +) + one who's afraid in A (+ what is afraid of in G):
Anu je strah zmija. Ana is afraid of snakes.
Anu je bio strah zmija. Ana was afraid of snakes.
Anu je bilo strah zmija. (the same meaning, more common)
The noun strah fear is the subject, as you can see from the past tense, but the sentence is usually treated as impersonal, so using neuter singular in the past is actually more common. As with other expressions where the person who feels something is not in the nominative case, the person is nevertheless usually placed at the first position.
There's one more way, not much used in speech, more in writing – the verb pair:
plašiti ~ u- scare
The verbs can be used in both ways:
Ana se plaši zmija. Ana is scared of snakes.
Anu plaše zmije. Snakes scare Ana.
You can also be afraid to do something – the just use an infinitive clause with any way of expressing fear:
Goran se boji voziti bicikl. Goran is afraid to drive bicycle.
Anu je strah roniti. Ana is afraid to dive.
On the other hand, there's just one verb to express expectation:
očekivati (očekuje) expect (+ A/clause)
It's simple to use – what is expected is in A:
Očekivali smo tvog brata. We expected your brother.
Now, all the constructs described above can be also used with clauses: you can both be afraid that something might happen or you can expect that something is going to happen.
All such clauses start with da and in principle can use any tense, e.g. future:
Ana se boji|
će biti hladno.|
The usual rules of word order in clauses apply:
Ana se boji [da¹ će² biti hladno]. Ana is afraid that it will be cold.
The verb očekivati (očekuje) expect is, of course mostly used to expect future events.
With both expectations and fear, it's common – but not obligatory! – to express future events with the present tense of perf. verbs. It's the twist: it's both OK to say:
Očekujem da će pasti kiša. 'I expect that rain will fall.'
Očekujem da padne kiša. (more or less the same meaning)
We have here used the perf. verb pasti (padne, pao) fall. Maybe there's small difference in meaning – if you use the present tense of perf. verbs, it's a bit less certain, and more speculative.
With the impf. verbs, it's not possible to use present tense to refer to future events in such clauses – if you use the present tense, it refers to ongoing processes:
Očekujem da će padati kiša. 'I expect that rain will be falling.' (later)
Očekujem da pada kiša. 'I expect that rain is falling.' (now)
(Of course, this applies to the verb (bude) as well, it behaves as any perf. verb here.)
The same holds for expressing fear, with an important detail – the third twist – if you use perf. verbs in present to refer to future, possible events, they must be negated:
Bojim se da će pasti kiša. 'I'm afraid that rain will fall.'
Bojim se da ne padne kiša. (more or less the same meaning)
This negation is "empty", it's just a grammatical feature. If we use a negative-demanding word as e.g. nitko, the sentence sounds wrong and ungrammatical:
(wrong) Bojim se da se nitko ne dođe. "I'm afraid that nobody will come."
That's because the negation has no effect, it's obligatory, but empty, it carries no meaning. The following sentence, is however, completely acceptable:
Bojim se da se netko ne dođe. I'm afraid that somebody might come.
Of course, the same automatic negation applies to (bude):
Bojim se da ne bude prekasno. I'm afraid that it might be too late.
Keep in mind that it's not mandatory to use (bude), you can use the present or the future tense of biti (je² +) be as well:
Bojim se da je prekasno. I'm afraid that it's too late.
Bojim se da će biti prekasno. I'm afraid that it will be too late.
Consequently, this means if you are afraid that something might not happen, you will have to use the future tense, where negation, if used, really has a meaning:
Bojim se da neće biti mjesta. I'm afraid there will/might be no room.
For impf. verbs, if there's a negation, it usually means that you are afraid of something not happening:
Bojim se da nemam vremena. I'm afraid that I have no time.
However, you will see sometimes empty negations even with impf. verbs – you have to apply your common sense then.
Since verbs behave so specially in clauses starting with da after verbs of fear, they are sometimes called fear clauses. (If by any chance, you know some Latin grammar, you should notice similarities!)
There's one more common verb that uses fear clauses:
brinuti (brine) (se²) care/worry
This verb has more uses and meanings, e.g. care and so on, but with clauses, it means worry. (According to the Standard, it should have an obligatory se², but it's often dropped in colloquial context.) For example:
Brinem se da ne zakasnim na posao. I worry that I'll be late to work.
Brinem se da ću zakasniti na posao. (about the same meaning)
The empty negation is completely automatic, most speakers are not aware of it at all (check the Examples).