Czech nouns inflect for case, gender and number.
Czech has seven cases: nominative, genitive, dative, accusative, vocative, locative, and instrumental inherited from Proto-Indo-European and Proto-Slavic. This essentially means that a word can have 14 possible forms in singular and plural.
Czech distinguishes three genders - masculine, feminine and neuter - and the masculine gender is subdivided into animate and inanimate. With few exceptions, feminine nouns in the nominative case end in -a, -e, or a consonant; neuter nouns in -o, -e, or -í, and masculine nouns in a consonant.
Nouns are also inflected for number, distinguishing between singular and plural. Although Czech grammatical numbers are singular and plural, several residuals of dual forms remain, such as the words dva ("two") and oba ("both"). Some nouns for paired body parts use a historical dual form to express plural in some cases:
ruka (hand) - ruce (nominative)
oko (eye) - oči
There are no articles in the Czech language.
Adjectives in the Czech language must agree in case, gender and animacy with the nouns they modify. Adjective declension also varies according to the gender of the noun which they are related to:
mladý muž (masculine) - a young man
mladá žena (feminine) - a young woman
mladé víno (neuter) - new wine
The comparative is formed by the suffix -ejší, -ější, -ší, or -í (there is no simple rule which suffix should be used).
The superlative is formed by adding the prefix nej- to the comparative.
krásný - krásnější - nejkrásnější (beautiful - more beautiful - the most beautiful)
tenký - tenčí - nejtenčí (slim - slimmer - the slimmest)
There are also short forms in some adjectives. They are used in the nominative and are regarded as literary in the contemporary language.
Unlike Czech adjectives and nouns, Czech adverbs have neither gender nor case: they do not change form.
Many adverbs must simply be memorized as individual words. Adverbs derived from adjectives, however, have certain regular paths of formation. Many Czech adverbs formed from adjectives end in -ě/-e: the adjectival ending drops, and -ě/-e is added in its place.
krátký - krátce - briefly
If an adjective ends in -ský or -cký, the corresponding adverb ends in -sky or -cky. This type of adverb includes many words referring to languages.
český - česky - Czech
Some other adverbs formed from different adjectives end in -o.
dlouhý - dlouho - for a long time
The Czech language has the same types of pronouns as many other languages: personal (ty, on), possessive (můj, tvůj), demonstrative (ten, tento), reflexive (se), indefinite (některý, nějaký) and interrogative (kdo, co).
Personal pronoun declension is complicated, some are declined according to adjective paradigms, some are irregular.
Czech uses personal pronouns less often than some other languages, including English, French or German, because pronouns are not required to determine the gender in the sentence. The Czech language uses other means to do that, like endings, prefixes and modifications of the verb that is used in the sentence.
Czech is a null-subject language, i.e. the subject (including personal pronouns) can be omitted if known from context. The person is expressed by the verb:
já dělám - dělám - I do
Czech verbs agree with their subjects in person (first, second or third), number (singular or plural) and in constructions involving participles also in gender. They are conjugated for tense (past, present or future), mood (indicative, imperative or conditional), aspect (perfective and imperfective), and voice (passive and active).
Czech verbs are distinguished by aspect: they are either perfective or imperfective. Perfective verbs indicate the finality of the process. Therefore, they cannot express the present tense. Perfective verbs are usually formed adding prefixes to imperfective verbs:
psát (imperfective) - to write, to be writing
napsat (perfective) - to write down
Czech verbs have three grammatical moods: indicative, imperative and conditional. The imperative mood is formed by adding specific endings for each of three person-number categories: -ø/-i/-ej for second-person singular, -te/-ete/-ejte for second-person plural and -me/-eme/-ejme for first-person plural. Imperatives are usually expressed using perfective verbs if positive and imperfective verbs if negative.
The conditional mood is formed with a particle after the participle ending in -l which is used to form the past tense. This mood indicates hypothetical events and can also be used to express wishes
Most Czech verbs fall into one of five classes, which determine their conjugation patterns.
Every Czech preposition determines the grammatical case and therefore the ending of the noun that follows it. It may be a good idea, although a somewhat hard task, to memorize which case each preposition is used with. One preposition can sometimes be used with several different grammatical cases having a different meaning each time.
Here are some common Czech prepositions and the cases they are used with: bez, od, u (genitive), k, kvůli, proti (dative), na, o, pro (accusative), na, v (locative), nad, pod, s (instrumental).
This is a very brief overview over Czech 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 Czech grammatical system and the main points you should consider when learning.