How do you work out whether a Russian word is masculine, feminine, or neuter?
Most nouns ending in -а or -я are feminine: мама, тётя, душа, Мария. Although quite a few such words are masculine: папа, дядя, Юра, юноша. Some can be either masculine or feminine: ябеда, соня, Саша, Женя.
Most nouns ending in -о, -е or -ё are neuter: молоко, поле, копьё, Домодедово, пальто, ателье.
Most nouns ending in a hard consonant or -й are masculine: стол, мяч, Пётр, кристалл, герой, литий, Сергей.
Nouns ending in -ь (the soft sign) can be either masculine конь, путь, царь or feminine: любовь, ночь, Сибирь. See this answer on how to tell them apart.
Foreign names and recent loanwords may not follow these rules. E.g. мисс ('Miss') is expectedly feminine and месье ('Monsieur') is masculine.
As far as I know, just about the only absolute rule is "If it ends in a hard consonant, it's masculine." (Note: this isn't the same thing as "If it's masculine, it ends in a hard consonant.")
The other rules are almost always true. So words ending in а/я are feminine, except for masculine nouns like мужчина, plurals like дома, and super exceptions like дитя which is neuter!
Nouns ending in -ь are also feminine, except for nouns like путь which are masculine.
Nouns ending in -о/е/ё are neuter, except for кофе which is also masculine!
As was said before, normally in reference to the singular:
words that end in a consonant (including й) are masculine. The only exceptions I can think of are foreign female names (like Kate - Кейт).
words that end in -o, -e are neuter and may be invariable (if adopted) or declinable. The only exception (other than foreign proper names) I can think of is "кофе" (it was кофий a couple of centuries ago and perfectly matched the masculine, and than changed to more-English кофе, while retaining its masculine gender, so it goes against the language. But most natives mindlessly treat it as a neuter, so the neuter eventually became the academic norm).
words that end in -у, -ю, -э are neuter and invariable (adopted)
words that end with -ы, -и are either plural or an adopted invariable neuter
words that end with -а, -я are feminine. There's a group of exceptions that end with -мя and are plural (время, знамя, пламя, вымя...). Also, if the word refers to a person with a known male gender, then it's definitely masculine (although it will decline just like a feminine); usually relatives: папа, дядя, дедушка and personal names such as Илья, Никита, especially short ones, but there are others (судья).
words that end with -ь may be feminine or masculine and should be looked up: "лань" is feminine, but "конь" is masculine. But if it ends in one of the sibilants -шь, -жь or -чь, it's feminine: мышь, блажь, картечь.
It seems strange to me that no one pointed out that in Russian, grammatical gender should always correspond with physical gender. So папа, дядя, дедушка, парниша, юноша are masculine, despite the ending, because they mean male persons. Конь is masculine and лошадь is feminine because this words mean male and female horses. Same with names: Никита, Данила are masculine, foreign names like Джейн, Кэтрин are feminine. If you know the physical gender you already know the grammatical gender
There's such a thing as three (and a half) types of noun declension. This is more important for words matching. And this declension (a) is defined by word endings, and (b) applies some restriction to gender.
When Russians see the word "хрень" — it's 3rd declension and thus can only be feminine.
When Russians see the word "кофе" — it's 1st declension and since it ends in "-e" (a "soft vowel"), it can only be neuter. (Academia at one point pushed to change the gender to masculine which only created a mess. Now it can be of either gender.)
If the word has an ambiguous ending, like "чупута" (it's just a set of letters), which is 2nd declension and can be of either feminine or male gender — it can be used as either: "Чупута убежал" or "Чупута ушла" and both phrases will sound correct.
One main thing that English speakers should keep in mind is that gender and "essence" are separate and independent concepts in Russian. the "neuter gender" isn't "it" — it implies that "no gender applies".
Of course, native speakers don't "work out" declensions, they just "feel" them.
There's only one way to identify a noun's gender 100% accurately: look up in your dictionary. However, there are some more or less reliable patterns:
- If a noun ends with -a/-я, this is the so called “feminine” type or feminine declension. As you might already have guessed, the majority of nouns in this group are feminine. Some masculine nouns may end in -a/-я. Those nouns mostly refer to people, namely family members (папа, дядя), professions (судья) or proper names (Ваня, Никита). Please note: There's a small group of neuter nouns that end in -мя: пламя, время among others.
-a/-я - most likely feminine, unless it refers to a male person or ends with -мя (that would be neuter). One exception: кофе (coffee) is masculine, though some dictionaries say the neuter is acceptable, too.
- If a noun ends in a consonant sound or the soft sign (-ь), this is the masculine declension because most of the nouns in this group are masculine: банк, танк, конь, огонь. However, the soft sign is tricky. Quite a large group of Russian feminine nouns end in the soft sign, too, so whenever you see a soft sign, check the dictionary for gender.
Consonant - masculine; soft sign - check the dictionary.
- o/ -e are the common endings of the neuter gender. Also, those weird nouns ending in -мя are neuter.
An answer that works every single time (no exceptions ever) is to look at the endings of adjectives or pronouns that are allowed to modify the noun: большое здание, so здание is neuter, мой папа, so папа is masculine. That is, when the adjectives or pronouns that modify a noun have masculine (resp, feminine or neuter) endings then the noun is masculine (resp. feminine or neuter). This could be considered the definition of the gender of a noun. It looks rather indirect, which makes it a conceptually interesting way to think about the issue, but this way of explaining the gender of nouns is impractical to non-fluent speakers who are seeking rules to help guess the gender of an unfamiliar noun. That is why it is more common to see rules based on the ending of the noun. Such “simpler” rules always come with exceptions.