In Russian to form the plular in nominative case (initial, dictionary form) we usually use endings –и or –ы.
1. In general case:
In masculine nouns add –и or –ы:
студент — студенты (student – students)
врач — врачи (doctor – doctors)
In feminine nouns –а and –я become –ы and –и:
стена — стены (wall – walls)
студентка — студентки (student – students feminine)
We add –и after letters г, к, х, ш, щ, ч and instead of ь:
ручка — ручки (pen – pens feminine)
карандаш — карандаши (pencil – pencils masculine)
конь — кони (horse – horses masculine)
дверь — двери (door – doors feminine)
In neutral nouns -о becomes -а and -е becomes -я:
окно — окна (window – windows)
море — моря (sea – seas)
Exception: яблоко (apple) in plural is яблоки.
2. There are particular cases of plural formation. For example, the word дерево (tree) in plural is деревья.
In some words there is omission or alternation of letters:
друг (friend) — друзья
парень (guy) – парни
кусок (piece) — куски
Remember following plural forms:
брат (brother) — братья
сын (son) — сыновья
стул (chair) — стулья
дом (house) — дома
город (city) — города
адрес (address) — адреса
номер (number) — номера
человек (person) — люди (people)
ребенок (child) — дети
дочь (daughter) — дочери
сестра (sister) — сестры
Sometimes in the plural form the stress shifts from the first syllable to the last syllable like in the words город (city) — города and адрес (address) — адреса, or vice versa: окно — окна (window – windows).
3. There are also nouns that only have a plural form:
часы – clock, watch
деньги – money
очки – glasses
брюки – pants
ножницы – scissors
And also those that only have a singular form:
молоко – milk
мука – flour
etc.
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