Grammar hook - mobile stress and the ё surprise

Russian stress is mobile and unpredictable - it moves between syllables as a word changes form. Сестра is stressed on the last syllable: сестрА. But the plural is сёстры - stress jumps to the first syllable, and the unstressed е transforms into ё.

This isn't random. When stress moves onto an е, it always becomes ё (which is by definition always stressed). The same pattern hits other common words: жена → жёны (wife → wives), звезда → звёзды (star → stars).

There's no rule predicting which words have mobile stress - you learn it word by word. But once you know the pattern exists, the ё stops being a surprise and starts being a clue: if you see ё, stress is right there.

Ways to say "sister"

RussianPronunciationEnglishNotes
сестраsestrasisterfem.; pl. сёстры
сестрёнкаsestryonkalittle sister (affectionate)fem.; for younger sister
сестричкаsestrichkasister (cute diminutive)fem.; warm, sweet
старшая сестраstarshaya sestraolder sisterage always specified
младшая сестраmladshaya sestrayounger sisterage always specified

Declension of сестра

CaseSingularPluralNotes
Nominativeсестрасёстрыstress shifts + ё
Genitiveсестрысестёрgen. pl. with fleeting ё
Dativeсестресёстрам
Accusativeсеструсестёрanimate = genitive
Instrumentalсестройсёстрами
Prepositionalо сестрео сёстрах

Sister in context

Моя старшая сестра учится в университете.
Moya starshaya sestra uchitsya v universitete.
My older sister studies at university.
старшая (fem.) agrees with сестра (fem.); в + prepositional
У меня две сестры.
U menya dve sestry.
I have two sisters.
две + genitive singular: сестра → сестры (not сёстры - number agreement)
Сестрёнка, я тебе звонила!
Sestryonka, ya tebe zvonila!
Little sis, I called you!
звонить + dative: ты → тебе; звонила (fem. past) - speaker is female
Она похожа на свою сестру.
Ona pokhozha na svoyu sestru.
She looks like her sister.
на + accusative: сестра → сестру; свою (fem. acc.) - reflexive possessive
Cultural context

Age order is always specified. In Russian family talk, saying just "моя сестра" (my sister) without старшая (older) or младшая (younger) feels incomplete. People will immediately ask "Она старше или младше?" (Is she older or younger?). Birth order shapes expectations - the старшая сестра (older sister) is expected to help, protect, and set an example.

Сестрёнка implies warmth and youth. While сестра is neutral, сестрёнка specifically suggests a younger sister and carries strong affection. An older sibling calling a younger one сестрёнка is common and endearing. Сестричка is even softer - almost exclusively used for very young sisters or in emotional moments.

Медсестра is not your sister. The word медсестра (literally "medical sister") means "nurse." It's a compound of мед- (medical) + сестра, reflecting the historical role of nuns and sisters in hospital care. Don't confuse it in medical contexts.

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