Syntax
What to master
Syntax studies phrases and sentences. You must find the grammatical base, distinguish subject and predicate types, identify secondary members, and classify sentences as simple or complex, one-member or two-member, extended or unextended. Know coordination and subordination, types of subordinate clauses, homogeneous members, detached members, introductory words and appeals. Also study direct and indirect speech, quotation, and syntactic norms such as agreement and government.
Traps
Questions often exploit homonymous conjunctions and allied words: что may be a conjunction or a relative pronoun. Compound conjunctions can be split (потому что, так как), so do not treat the first part as a separate clause marker. With homogeneous predicates, a shared object may require different cases: любить и увлекаться (чем?) - not любить и увлекаться музыкой without adjustment. Do not confuse a subordinate clause with a detached participial phrase. In agreement, check the head noun, not the nearest word.
Worked example
In «Когда я вернулся, она уже ушла», the comma closes the subordinate clause and separates it from the main clause. The grammatical bases are я вернулся and она ушла. Rule of thumb: first mark all bases, then find boundaries and connectors; this prevents inserting commas inside a base.
Rule of thumb
Parse from the grammatical base outward: bases → boundaries → connectors → punctuation.