Substantivoj

Substantivoj are the nouns of Esperanto. They designate persons, places, things, or ideas and form a central category of words used to name referents in discourse. Nouns in Esperanto are gender neutral; there is no grammatical gender, and most nouns can stand as the subject, the object, or the complement in a sentence.

In Esperanto, the base form of a noun ends with the vowel -o. The plural is indicated with the suffix -j, giving forms such as substantivoj (nouns) and domoj (houses). The accusative case is marked by adding -n to the noun, and if adjectives or adjectives that modify the noun are present, they also receive -n when expressing direct objects (e.g., granda domon). There is no separate indefinite article; the definite article la is used for both known and given nouns, and numerals or demonstratives may precede the noun.

Adjectives agree with nouns in number and case. An adjective used with a singular noun ends in -a (bela, granda); in the plural it ends in -aj (belaj, grandaj); in the accusative it ends in -an or -ajn accordingly (belan, belajn; grandan, grandajn). The adjective follows the noun, but the order can vary in poetic or emphatic contexts. Nouns form the basis for many derived terms through affixes, such as -eco (quality), -ulo (person), -aro (group), and -ist (member or advocate), enabling a productive word-formation process without changing the core noun.

Proper nouns are capitalized and behave like common nouns in syntax, but they do not carry grammatical gender and follow the same plural and accusative rules when used in sentences. Substantivoj thus function as the backbone of Esperanto vocabulary, enabling clear and flexible expression.