For some reasons I really don't understand, basic pronouns ("I", "he") are always explained together with forms of verb "to be" — "I am", "he is", etc., and that's usually the first thing someone learns. I've postponed explaining such things... until now. So, there is a formula how to use pronouns + "to be" in Croatian.
As I have already explained, pronouns are almost always omitted in Croatian. However, they are frequently used with the present tense of "to be" (reasons will become obvious later), so it is convenient to describe them together.
This will enable you to produce sentences of type "X is Y", like "the apple is yellow", "Ana is a girl", "keys are in the drawer", etc.
Croatian has three "persons" (same as English) — 1st, 2nd, and 3rd. First two persons are about sides of conversation, the third one about everything else. Here are forms of verb "to be" together with personal pronouns in nominative:
person m n f 1st sg. ja säm "I am" 2nd sg. ti si "you are" 3rd sg. on je "he is" ono je "it is" ona je "she is" 1st pl. mi smo "we are" 2nd pl. vi ste "you are" 3rd pl. oni su "they are" ona su "they are" one su "they are"
The verb does not distinguish gender — only 3rd person pronouns do. Their forms should remind you of adjectives or nouns, since the endings are the same. Dots over ä in säm should remind you that the a is lost in other forms; this is my invention, normally this a is spelled and pronounced as any other a.
Again, English is a peculiar language, it does not distinguish singular and plural in the 2nd person — both are "you are". Croatian and other most languages does distinguish. ti is used when talking to one person, vi to more than one person. Likewise, Croatian has one "your" for singular, another for plural, all verbs have different forms for singular and plural in the 2nd person, etc.
Pronouns also have forms for other cases — the above forms are for nominative only. We'll learn other cases later, in 18 Basic Cases for Pronouns.
What basic sentences can we make with personal pronouns and this verb? There are several types of sentences that fit into "x is y" model. In such sentences, both nouns (or phrases) are in nominative. They can express what is something or someone. For example:
Zagreb je veliki grad. "Zagreb is a big city."
Ja säm student. "I am a (university) student (male)."
Ja säm studentica. "I am a (university) student (female)." (female speaker)
Ti si malo dijëte. "You are a small child."
On je novi poštar. "He is the new postman."
In such sentences, pronouns are rarely omitted. You maybe noted that adjectives in nom.sg.m form in these sentences has always -i. That's one of subtleties, but it's not always respected in colloquial speech. There's a special word for "female student" so we must use it if we talk about somebody who is female.
Then, one can just talk about properties or states of something or somebody:
Zagreb je velik. "Zagreb is big."
Ja säm žedän. "I am thirsty." (male speaker, ja refers to m gender)
Ja säm umorna. "I am tired." (female speaker, ja refers to f gender)
Ja säm gladän. "I am hungry." (male speaker)
Mi smo umorni. "We are tired."
Noći su duge i hladne. "Nights are long and cold."
Now adjectives should never have an -i, but again it's not always respected in real life.
There's something important: although ja doesn't distinguish gender, you still have to adjust the adjective to the gender 'hidden' behind that ja. This is similar to Romance languages like Spanish:
(Spanish) Estoy cansado. "I am tired" (male speaking)
(Spanish) Estoy cansada. "I am tired" (female speaking)
But what about plural? If there's a group of women only, you should use adjectives and pronouns in f gender; otherwise, for mixed or male-only groups, you should use m gender:
Vi ste gladne. "You are tired." (speaking to a group of women)
Vi ste gladni. "You are tired." (speaking to a general group)
Usually, in such sentences, one omits the personal pronouns, but must place säm, si, je... after the adjective (or adjective phrase), at the second place in a sentence. This does not hold for verbs in general, only for forms säm, si, etc.:
Check how the pronouns were omitted in the Spanish examples as well (but the verb is out to the first place). Here are the basic adjectives standing for properties, including some states like gladän "hungry":
kratäk "short" (length)
nizäk "low"; "short" (people)
vruć "hot" (temperature)
Adjective kratäk just means "short in length", while low height of both buildings and people is expressed with nizäk. Also, observe how some adjectives have an a that's lost whenever an adjective gets any ending (here marked as ä).
Next, we can say where is something/someone, using u + dat. or na + dat. For example:
Iva je u Zagrebu(D). "Iva is in Zagreb."
Nož je u ladici(D). "The knife is in the/a drawer."
Tanjur je na stolu(D). "The plate is on the table."
Furthermore, there are impersonal sentences, talking about the "current situation"; English uses a dummy pronoun "it", but Croatian never uses any pronouns in such sentences. Also, observe the placement of the verb — it again goes to the second place. Adjectives must be in neuter gender in such sentences:
Hladno je. "It is cold." (lit. "is cold."
Hladno je u sobi. "It is cold in the room."
U sobi je hladno. (just different order of words)
Käsno je. "It is late."
Vruće je. "It is hot".
Ti vs. Vi
There's an additional twist. In Croatian, you cannot say ti to anyone, just to people you're friend with, your family, etc. To everyone else you should (should, not must: this is a social convention) use the plural pronoun — vi. But it means that all other words, like verbs etc. must be in the plural as well! So, you talk to "people you respect" in exactly the same way as addressing a group of people! Even more, such a 'honorific' vi is always written capitalized (Vi). For instance:
Ti si doktor. "You are a doctor" (talking to a person you're friend with)
Vi ste doktor. "You (sir/madam) are a doctor" (talking to a person you respect)
Vi ste doktori. "You (guys) are doctors" (talking to a group)
If you use such 'respectful' Vi, adjectives should be always in pl. masculine, regardless of the gender (at least, this is the standard):
Vi ste gladni. "You (sir/madam) are hungry" (talking to a person you respect)
Children use ti always among themselves, but gradually learn to say Vi to older non-relatives. People in a shop, a bank, workplace address each other with a Vi. One addresses only people he/she works with a longer time with a ti.
There's a possibility to say that something is "not". With forms of the verb "to be", Croatian always uses special forms of the verb, which are simply obtained by adding a ni- to the forms of the verb listed above:
Zagreb nije veliki grad. "Zagreb is not a big city."
Ja nisäm student. "I am not a (university) student (male)."
Ja nisäm studentica. "I am not a (university) student (female)." (female speaker)
Ti nisi malo dijëte. "You are not a small child."
On nije novi poštar. "He isn't the new postman."
Nož nije u ladici. "The knife is not in the drawer."
Forms nisäm etc. don't have any special place in a sentence, they are usually put to the beginning of a sentence if the personal pronoun is omitted (this includes impersonal sentences!):
Nisäm žedän. "I'm not thirsty."
Nisäm gladna. "I'm not hungry." (female speaking)
Nismo umorni. "We're not tired."
Nije hladno. "It is not cold." (lit. "is not cold.")
Nije hladno u sobi. "It isn't cold in the room."
Nije käsno. "It's not late."
We can put adverbs into such sentences (and most other sentences) to give additional information. Adverbs do not change through genders, numbers and cases. Here are the basic adverbs.
Adverbs of probability are used to express how probable some statement is. The most used ones are:
adverb meaning možda "maybe" vjërojatno "probably" sigurno "certainly"
They are usually put after the verb:
Iva je možda u Zagrebu. "Maybe Ivan is in Zagreb."
Nož je vjërojatno u ladici. "The knife is probably in the drawer."
Ti si sigurno gladna. "You are certainly hungry." (speaking to a female)
When pronouns are omitted, these adverbs are usually placed at the beginning (the verb goes again to the second place):
Sigurno si gladna. "You are certainly hungry." (speaking to a female)
Vjërojatno je hladno. "It's probably cold."
Next, there are adverbs of repetition (this is the name I invented). They express whether there were such states in the past, or will there be in future. Sounds complicated, but such adverbs are in fact simply:
adverb meaning opet "again" ponovo ponovno
adverb meaning prvi put "for the first time" drugi put "for the second time" zadnji put "for the last time" posljëdnji put
Some of them are really a small phrase, more than one word, but function as an adverb and should not be split. Adverb ponovo has an alternative form ponovno and some people prefer the latter. They are placed in a sentence the same way adverbs of probability are. For example:
Opet nisäm gladna. "Again I'm not hungry." (female speaking)
Ivan je opet žedän. "Ivan is thirsty again."
Ponovo je hladno. "It's cold again."
Ana je prvi put u Londonu. "Ana is in London for the first time."
Drugi put smo u Zagrebu. "We're in Zagreb for the second time."
There are also adverbs of intensity (also known as "adverbs of degree" or "intensifiers") that modify the "strength" of a property or state:
adverb meaning adverb meaning malo "a bit" jako "very" pomalo "somewhat" dosta "considerably,
potpuno "completely" prilično posve strašno "terribly" (colloquial)
Out of them, jako is the most often used, turning e.g. "hungry" into "very hungry". Adverb strašno is colloquial, similar to English "terribly". Placing is as with other adverbs:
Ivan je jako žedän. "Ivan is very thirsty."
Ana je dosta umorna. "Ana is quite tired."
Noći su prilično duge. "Nights are quite long."
Strašno säm gladän. "I'm terribly hungry." (male speaking)
Finally, there's a hard-to-translate intensifier baš. It's not very formal, but it's often used in speech. When used with properties or states, it means roughly "really":
Ivan je baš žedän. "Ivan is really thirsty."
Baš je hladno. "It's really cold."
Observe how adjectives adapt to nouns, but adverbs do not. If more than one adverb is used, adverbs of intensity will come before the property, other adverbs will come before them or at the beginning of a sentence if pronouns are omitted:
Ivan je opet jako žedän. "Ivan is very thirsty again."
Ponovo je dosta hladno. "It's quite cold again."
Warning: if you want to say "Ivan is cold" meaning "Ivan feels cold", you cannot say it like Ivan je hladän. There's a special construct in Croatian for such things, described in 18 Basic Cases for Pronouns. This holds for vruć "hot" as well.
Updated 2014-09-17 (v. 0.4)