What are Nouns?

This does not mean that running is considered an abstract substance; however, it does mean that it is treated as such for the purposes of grammar. Consider this table:

The black phrases in the table above are grammatical; the red ones are not. As you can see, the deverbal nouns running and (a) run are treated by English grammar the same as nouns referring to substances and objects, respectively. In fact, all nouns are divided into those that may be pluralized and those that may not. The latter refer to things as indivisible wholes, whether they be objects, actions, or qualities. The former refer to things as countable entities: objects, actions, or qualities. Remember: 'noun' is not a category of real things in the world; it is a grammatical category, a way of treating semantic categories for the purposes of grammar. 'Noun', therefore, is a grammatical category that treats all things in the world as countable (objects) or uncountable (substances).

Russian nouns are similar to English nouns in that they reflect number in their form, e.g. стол "table" versus столы "tables". They differ from English nouns, however, in two respects. First, Russian nouns also express declension class in their form and some express gender. Gender is a grammatical category that indicates the sex of the object referred to by the noun (its 'referent'). The indicator is the ending -a in the singular, e.g. брат "brother", with no ending, but сестр-а "sister". The -a (or -я) reflects the fact that the second word refers to a female.

Not all nouns that end on -a, however, refer to females. All nicknames, for example, whether referring to males or females, end on this ending: Маш-а "Masha" (nickname for Мария "Mary") but also Алёш-а, the nickname for Алексей "Alexis". In fact, Саша is the nickname for both Александр "Alexander" and Александра "Alexandra" and Женя "Zhenya" is the nickname for both Евгений "Eugene" and Евгения "Eugenia". On the other hand, certain nouns referring to professions, such as профессор "professor", доктор "doctor", директор "director" have no -a but may refer to either males or females. So (natural) gender is expressed imperfectly in the Russian grammatical system, but it expressed.

Declension class is an arbitrary class to which all but a handful of nouns belong. Words which end on a hard consonant or the vowels o or e belong to Declension I, e.g. стол "table", муж "husband", окно "window", поле "field". Some nouns ending on soft consontants also belong to Declension I, e.g. учитель "teacher", портфель "briefcase". Nouns ending on a or я belong to Declension II. These include книга "book", полка "shelf", сестра "sister", жена "wife" but also папа "daddy" and дядя "uncle". Many, probably most nouns ending on a soft consonant or мя belong to Declension III: кость "bone", площадь "square" and имя "name", время "time". Declension IV is used primarily to mark the plural but many singular nouns belong to it, including ясли "nursery school", чернила "ink", ворота "gate", новости "news". Declension IV nouns usually end on ы or и, but many end on a and some end on e.

The indeclinable nouns are exceptional borrowed words, usually ending on an odd vowel, not recognized by Russian grammar: у, и, е but also o. (Borrowed words ending on a are usually treated at Declension II nouns, since nouns in that declension typically end on a.) Some common words with no declension class (thus no case endings and hence their name: 'indeclinable nouns') are пальто "overcoat", кофе "coffee", кафе "cafe", кенгуру "kangaroo", кино "movie theater", такси "taxi", атташе "attache".

While natural gender as defined above is not consistent in Russian, grammatical gender is. Grammatical gender is another word for 'agreement', a category reflected in adjectives and verbs that 'agree' with nouns. Agreement in this sense refers to a variable set of endings added to adjectives and past tense verbs to express, not the gender of the adjectives and verbs, but a noun with which they are closely associated. In English, for example, when we say red car, the adjective red is an attribute of car. When we say the car is red, red is a predicate of car. Both these relations require grammatical agreement in Russian. So, if the noun is grammatically feminine, the adjective must be feminine; if the noun is grammatically masculine, the adjective must be, too. Here are some examples.

The underlining shows how each adjective ending 'agrees' or identifies with the noun it is associated with. All adjectives must sport a particular ending expressing a grammatical agreement class, usually called masculine, feminine, neuter, and plural–although these are not descriptive names and are only obliquely related to natural gender.

Well, that's a fair question: how is agreement related to natural gender and declension class? Agreement is determined by the following algorithm:

1. If the noun has (natural) gender, assign feminine agreement for feminine nouns and masculine gender for masculine nouns;
2. If the noun does not have gender, assign agreement as follows:
   • Masculine agreement to Declension I nouns ending on a consonant;
   • Neuter agreement to Declension I nouns ending on o or e and Declension III nouns ending on мя;
   • Feminine agreement to Declension II nouns and Declension III nouns ending on soft consonants;
   • Plural agreement to Declension IV nouns.
3. If the noun is indeclinable, assign Neuter agreement.

What this means is that if a noun refers to a male, regardless of its declension class, agreement is masculine:

Notice that even if the noun does not belong to any declension class, like атташе and кенгуру, it still commands agreement if it refers to a sexually differentiated animal. (If the noun refers to an sexed animal but you don't know the sex, use masculine.) The ending on the noun means nothing if the noun refers to a male or female.

If the noun does not refer to an animal, but to an inanimate object, agreement then defers to declension class, following the list above. In the absence of a declension class (indeclinable nouns), neuter agreement is assigned.

Notice we have added the verbal agreement pattern to this table to complete the picture of agreement in Russian. Adjectives have their own agreement endings but verbs do not, so they just borrow those of the nouns. Adjectives require a more complex agreement system than verbs since they must also express case. Verbs simply agree, so they need only endings for the four basic agreement categories: feminine, masculine, neuter, and plural.