Nominative subject

1. The Subject and the Nominative Case
The nominative case is the default form you find in a dictionary. Its main job is to mark the subject of a sentence. It tells us who or what is performing the action or being described, answering the questions Kdo? Co? (Who? What?). The nominative is also used with the verb být (to be) to describe permanent identities like nationalities or qualities, as well as in constructions like to je + nominativ. When stating professions, the nominative is the standard, neutral choice (Petr je učitel). The instrumental case is often a more formal alternative or used to emphasize an acquired function or role (Petr je učitelem). Furthermore, verbs of becoming like stát se require the instrumental when followed by a noun, as seen in být / stát se + instrumentál. If the word following stát se is an adjective, the instrumental is the standard choice (e.g., stal se opatrnějším), while the nominative is less common. For the verb být, standalone adjectives describing the subject are typically in the nominative case (e.g., Petr je nemocný). However, adjectives modifying an instrumental noun must agree in the instrumental (e.g., Petr je dobrým učitelem), and adjectives acting as nouns can also take the instrumental (e.g., Petr je vedoucím oddělení). Crucially, the nominative case is never used with primary prepositions. If a noun follows a basic preposition, it is not in the nominative.

2. Agreement and Dropped Pronouns
The nominative subject dictates how the verb changes to match the person, number, and (in the past tense) gender. In the plural past tense, the subject's gender and animacy determine the specific verb ending (-i for masculine animate, -y for masculine inanimate and feminine, -a for neuter). Additionally, any adjectives, pronouns, or numerals modifying the subject must also be in the nominative case and agree with it in gender and number. However, there is a crucial exception for numerals 5 and above (and quantifiers like mnoho). When these act as the subject, the counted noun is forced into the genitive plural, and the verb must take the neuter singular form (e.g., Pět mužů tam bylo). Because the verb ending clearly shows who is doing the action, Czech often drops pronouns. This means you should usually omit nominative personal pronouns unless you need to emphasize them or create a contrast.

3. Word Order vs. Endings
In English, the first noun is almost always the subject. In Czech, basic SVO order is common, but word order is highly flexible and used to show emphasis. You usually identify the subject by its nominative ending and the verb's form, not just by its position. For example, in the sentence Knihu čte student, the word student is the nominative subject even though it appears at the end. However, when nominative and accusative endings are identical (which is a major feature across multiple genders, including all neuter nouns, all masculine inanimate nouns, many feminine nouns, and even some masculine animate nouns), word order or context is used to identify the subject.

4. Other Uses
The nominative is also used for naming things. This includes giving your name with the verb jmenovat se (e.g., Jmenuji se Petr). Crucially, when a proper name, title, or brand is attached to a generic noun, it stays frozen in the nominative case even if the generic noun changes its form (e.g., v hotelu Hilton, čtu knihu Harry Potter). It is also used for standalone exclamations. Furthermore, the nominative is used after conjunctions like jako (as/like) and než (than) when comparing the subject to something else (e.g., Pracuje jako učitel, Petr je starší než Pavel). Note that in standard Czech, the nominative is not used for directly addressing or calling someone; for that purpose, you must use the vocative case. However, the nominative form is identical to the vocative for all plural nouns, all neuter nouns, and all adjectives. Additionally, in colloquial spoken Czech, the nominative is frequently used instead of the vocative even for singular masculine and feminine nouns (e.g., pane Novák instead of pane Nováku).