My notes on Russian grammar, built around the thing that makes Russian Russian: the case system. English relies on word order to show who did what to whom; Russian frees the word order and instead changes the ending of the noun to mark its role.

The six cases at a glance

Every case has a function, a question word it answers, and trigger words that tip you off. Here they are on one noun, собака (sobaka, dog):

CaseQuestionFunctionсобака becomes
Nominativeкто? что? (who/what)the subject / dictionary formсобака
Genitiveкого? чего? (of whom/what)possession, absence, quantityсобаки
Dativeкому? чему? (to whom/for what)the indirect object, feelings, ageсобаке
Accusativeкого? что? (whom/what)the direct object, motion towardсобаку
Instrumentalкем? чем? (with whom/what)tool, “with”, professionsсобакой
Prepositionalо ком? о чём? где? (about/where)location and topic(о) собаке

Start here

  1. russian-case-system - the overview: why cases exist, what they each do, and the same noun run through all six. Read this first.
  2. Then the individual cases above, roughly in order of how often you meet them: nominative and accusative first, then genitive (everywhere), then dative, prepositional, and instrumental.

The one mindset that makes it click

Learn the usage before the endings. Understand when a case applies (what role the noun is playing) first; the endings are easier to absorb once you know why you are changing the word. Getting a case ending wrong rarely breaks meaning - a Russian will still understand you - but correct case is what makes the grammar right.