Serbian nouns are classified into three declensional types, denoted largely by their nominative case endings as "-a" type, "-i" type and "-e" type. Nouns of any of the three genders - masculine, feminine or neuter – may fall into any of these declensional types.
Each noun may be inflected to represent the noun's grammatical case, of which Serbian has seven: nominative, genitive, dative, accusative, vocative, instrumental, and locative.
Nouns are further inflected to represent the noun's number, singular or plural.
Adjectives in Serbian may be placed before or after the noun they modify but must agree in number, gender, and case with the modified noun.
velika kuća (feminine singular, nominative case) – a big house
jednim klikom (masculine singular, instrumental case) – with one click
Adverbs in Serbian are, unlike nouns, verbs, adjectives, pronouns and numbers, indeclinable words, similar to prepositions, conjunctions, exclamations and particles. These indeclinable words are added to verbs to determine the time, place, manner, cause, point and the amount of the action of the verb.
Some examples of Serbian adjectives: ovde/ovdje (here), napolju/vani (outside), gore (up), dole/dolje (down), sada (now), tada (then), nikada (never).
Pronouns, when used, are inflected along the same case and number morphology as nouns. Serbian is a pro-drop language, meaning that pronouns may be omitted from a sentence when their meaning is easily inferred from the text. In cases where pronouns may be dropped, they may also be used to add emphasis. For example:
Kako si? - How are you?
A kako si ti? - And how are you?
Like those of other Slavic languages, Serbian verbs have a property of aspect: the perfective and the imperfective. Perfective indicates an action that is completed or sudden, while the imperfective denotes continuous, repeated, or habitual action. Aspect compensates for a relative lack of tenses compared with e.g. Germanic or Romance languages. The verb already contains the information whether the action is completed or lasting, so there is no general distinction between continuous and perfect tenses.
Slavic verbs, in general, are characterized by a relatively low number of stems, from which a wide variety of meanings is achieved by prefixation.
Serbian verbs are conjugated in four past forms - perfect, aorist, imperfect, and pluperfect - of which the last two have a very limited use (imperfect is still used in some dialects, but the majority of native Serbian speakers consider it archaic), one future tense (also known as the first future tense, as opposed to the second future tense or the future exact, which is considered a tense of the conditional mood by some contemporary linguists), and one present tense. These are the tenses of the indicative mood.
Apart from the indicative mood, there is also the imperative mood. The conditional mood has two more tenses: the first conditional (commonly used in conditional clauses, both for possible and impossible conditional clauses) and the second conditional (without use in the spoken language - it should be used for impossible conditional clauses). Serbian has an active and a passive voice.
As for the non-finite verb forms, Serbian has one infinitive, two adjectival participles (the active and the passive), and two adverbial participles (the present and the past).
Serbian has a rich case structure that is reflected in the declension of nouns and adjectives, which allows for a great deal of freedom in word order.
In English, for example, the word order shows a difference in meaning between "Man bites dog" and "Dog bites man". In Serbo-Croatian, Čovjek grize psa and Čovjeka grize pas have the same word order, but the meanings are shown by the noun endings.
Any order of the three constituents is grammatically correct, and the meaning is clear because of the declensions. However, the usual order is subject–verb–object, as in English.
Each preposition in Serbian has an assigned case. If an inflectable word follows a preposition, the word is declined in the same case as the preposition's assigned case.
For example, prepositions od, do, iz take the genitive case and prepositions na, o, po require the noun to be in the locative case.
This is a very brief overview of Serbian grammar. To truly master it, you will need to study each of the parts of speech in much more detail. However, this overview will hopefully give you a general idea of the Serbian grammatical system and of the main points you should consider when learning.