Croatian often uses patterns of verb derivation where meanings are derived by simply adding prefixes. For instance, let's take the following verb pair:
padati ~ pasti (padne, pao) fall
From it, you can derive e.g. the following verb pairs with specific meanings:
ispasti (ispadne, ispao) fall out
raspadati ~ raspasti (raspadne, raspao) se² fall apart
upadati ~ upasti (upadne, upao) fall into
All such pairs are of the same kind like the base pair: there's a process (involving a kind of ‘falling’ that can be completed). But what about if we add pri- to the base pair:
pripadati ~ pripasti (pripadne, pripao) ?
The verb pripadati of course means belong, but what should the perfective verb mean? Belonging is a state; how can you complete it?
It turns out that the perfective verb is used, but in the meaning begin to belong, start to belong. For verbs that indicate lasting states, associated perfective verbs often mean entering the state.
Such verbs are often hard to translate into English. The verb pripasti (...) will be usually translated as given, assigned and so on, or the sentence would be rephrased.
Such perfective verbs that don't mean completion or accomplishment are sometimes called inchoative verbs (abbreviated as inch.).
To emphasize that the perfective verb has not the usual meaning of ‘completion’, but ‘getting into a state’, I'll use a double tilde (~~). The prefix za- is often used to make such verbs:
mrziti ~~ za- («) hate
pamtiti ~~ za- memorize
voljeti (voli, volio, voljela) ~~ za- («) love/like
Ana je zavoljela zeleni čaj. Ana started to love green tea.
Some pairs don't follow this scheme:
cvjetati ~~ pro- bloom
spavati ~~ zaspati (zaspi) sleep
shvaćati ~~ shvatiti understand, realize
sviđati se² ~~ svidjeti (svidi, svidio, svidjela) se² like
The verb zaspati has an alternative, non-standard pres-3 form zaspe that's quite common in more eastern regions of Croatia (and in Serbia, but it's nowhere accepted as standard). The perf. verb usually corresponds to English fall asleep:
Goran je brzo zaspao. Goran quickly fell asleep.
(Historically, the pair meaning sleep was also derived with just za-; however, the verb spati (spi) sleep is now archaic in most of Croatia; it has been replaced by more regular spavati, but the older verb is still used in some dialects.)
Some action verbs that have a meaningful start and completion of action, have two associated perfective verbs! For such verbs, I will list both perfective verbs:
Such groups of verbs can be called aspect triplets. Such common triplets are:
igrati ~ od- («) ~ za- («) play (game)
pjevati ~ ot- ~ za- sing
svirati ~ od- («) ~ za- («) play (music)
As you can see, the stress behaves the same in both perf. verbs. It really depends on the base verb.
While English often uses get + adjective to express entering a state, Croatian has specific verbs:
ogladniti («) perf. get hungry
ozdraviti perf. recover, get healthy
razboljeti (razboli, ...) se² perf. get sick
For some meanings, you can either make someone something, or get something; the second meaning requires a se² in Croatian:
rastužiti («) perf. make/get sad
razljutiti («) perf. make/get angry
razveseliti («) perf. cheer up
For some meanings in Croatian, there's a full verb pair that indicates getting into a state; the impf. verb sees entering a state as a process (e.g. it can take a while to become sick, it can take a while to get old, etc.):
pokretati (pokreće) ~ pokrenuti (pokrene) get moving
starjeti/stariti ~ o- grow/get old
Therefore, there are verb triplets with two verbs for entering the state: one impf. and another perf. A parallel in English would be:
I was getting hungry. = enter-impf.
I got hungry. = enter-perf.
I am hungry. = state (impf.)
There are three such triplets for body position verbs, one of them I've introduced in 52 Stand, Become, Exist, Cease; we can also list verbs be and become as a kind of triplet:
(legne, legao, legla)
There is one more type of perfective verbs, where action consists of bits – one example is sneezing: it's a sequence of individual sneezes. Croatian has verbs for both continuous sneezing and for a single sneeze:
kihati (kiše) sneeze (series)
kihnuti (kihne) sneeze (once)
Again, kihnuti (kihne) is a perf. verb – you cannot use it in the present tense, you cannot tell how long it took, and so on. However, there's no completion or accomplishment – only one ‘atomic’ event. To indicate such perf. verbs, I'll use a tilde with a small, superscript number one (~¹). Such verbs are:
kapati ~¹ kapnuti (kapne) drip
kucati ~¹ kucnuti (kucne) knock
štucati ~¹ štucnuti (štucne) hiccup
treptati (trepće) ~¹ trepnuti (trepne) blink
As you can see, such verbs frequently end in -nuti, with the regular -ne in pres-3. Perf. verbs with this ‘once’ meaning sometimes have a fancy name: semelfactive (abbreviated as smlf.); the corresponding impf. verbs are sometimes called iterative.
This doesn't apply to all verbs where it could make sense: for instance, there's no verb for "cough once".
There are verb pairs where the perf. verbs have meaning similar to ‘atomic’ – they mean for a short while, a bit. I will classify them as kind-of semelfactive, with the same mark (~¹), but you should be aware of the small difference. Three most common pairs like that are:
misliti ~¹ po- think
nadati se² ~¹ po- («) hope
osjećati ~¹ osjetiti feel
The perf. verbs above mean think for a short time and hope for a short time, or have a thought. They are often used in negative, to emphasize that somebody didn't think even for a moment.
Don't forget that there's a substantial difference in meaning between verbs like zavoljeti (...) and pomisliti. The former verbs indicate entering a state which can last any amount of time – we don't say how long, and if we want to express when the state ended, we have to use another verb. The latter ones are ‘atomic’, or small ‘pulses’, indicating that action or state lasted for a small amount of time:
(atomic / brief)
start to love
think for a moment
However, there are perf. verbs where the two meanings are mixed. Two common ones are:
From what I've explained above, you would expect that poželjeti (...) means wish for a moment, and that zaželjeti (...) start to wish, but it's not so – both have meaning somewhere in between, and are used interchangeably.
There are also secondary, ‘iterative’ impf. verbs derived from semelfactive verbs. For example:
pomisliti smlf. think for a moment → pomišljati («)
The relation of these two verbs is like kihnuti (...) vs. kihati (...) – the impf. verb stands for a series of individual short thoughts, with unspecified time between the thoughts (it could be hours, or days, or weeks, or more):
misliti impf. think
pomisliti smlf. think for a moment, once
pomišljati («) impf. think once a while
All three verbs are sometimes translated as think, which unfortunately hides various shades of meaning.
Finally, there are verb pairs that can be understood either as normal impf.-perf. pairs, or as iterative-semelfactive, depending on the context. Common pairs are:
bacati ~/~¹ baciti throw
pokazivati (pokazuje) ~/~¹ pokazati (pokaže) show
In fact, most perf. verbs also can be used in this way, for short events, while most impf. verbs can be also used for series of short events.