-a

Unlike masculine inanimate nouns (which do not change in the accusative), most singular masculine animate nouns take a specific ending when they are the object of a verb or certain prepositions like pro (for).

Because the accusative borrows the genitive forms (note that this rule applies strictly to the singular; plural forms are different!), here are the key rules for forming the singular masculine animate accusative:

• Hard Consonants: Nouns ending in a hard consonant, and many ending in an ambiguous consonant, add -a to the dictionary form (e.g., bratr → bratra, doktor → doktora, motýl → motýla).
• Fleeting 'e': If the noun ends in -ek or -el, the 'e' usually drops before adding -a (e.g., dědeček → dědečka, Marek → Marka, Pavel → Pavla, Karel → Karla), with exceptions like manžel (husband) which keeps the 'e' (manžel → manžela). The word pes (dog) also drops the 'e' to become psa.
• Vowel Shift: If the noun has ů in the final syllable, it often changes to o when adding the ending (e.g., bůh → boha, vůl → vola).

Other Endings:

• Nouns ending in a soft consonant, as well as some ending in an ambiguous consonant, take -e instead, and may also drop a fleeting 'e' or shift a vowel (e.g., učitel → učitele, otec → otce, kůň → koně).
• Nouns ending in -a take -u (e.g., předseda → předsedu).
• Most nouns ending in -e do not change (e.g., soudce → soudce).
• Nouns ending in -ý decline like hard adjectives and take -ého (e.g., známý → známého, vrátný → vrátného).
• Nouns ending in -í decline like soft adjectives and take -ího (e.g., průvodčí → průvodčího).

Special Cases and Colloquial Usage:

• Foreign Names: Latin and Greek names ending in -us or -os drop this suffix before adding -a (e.g., Kristus → Krista). Names ending in -o also take -a (e.g., Ivo → Iva).
• Colloquial Animacy: In spoken Czech, some biologically inanimate objects (especially food, drinks, and expressive terms) are treated as animate and take the -a ending (e.g., dát si panáka - to have a shot, dát si buřta - to have a sausage).

Remember that adjectives and pronouns describing the noun must also change to match it. Adjectives take -ého for hard endings (e.g., nový student → nového studenta) and -ího for soft endings (e.g., inteligentní student → inteligentního studenta). Pronouns also change, but often have their own specific forms (e.g., ten → toho, můj → mého). Also, grammatical animacy doesn't always mean 'biologically alive'—for example, sněhulák (snowman) is grammatically animate and becomes sněhuláka!