Basics. Defining vs. Non-defining Relative Clauses
Defining vs. Non-defining Relative Clauses
Relative clauses add detail to your sentences, but punctuation changes everything. A defining relative clause provides essential information to identify the noun without commas (e.g., "The wand that sparks purple magic is dangerous"). A non-defining relative clause adds extra, non-essential information and must be separated by commas (e.g., "My brand-new laptop, which I bought yesterday, is broken"). Additionally, the pronoun that can never be used in a non-defining clause!
In this challenge, you will navigate eccentric scenarios like a wealthy widow's will, an alien tour guide's Earth manual, and an HR manager's workplace disaster report. You will practice identifying when information is essential or extra, applying correct comma punctuation, and choosing the appropriate relative pronouns (who, which, that, whose, and where).
You'll work through 12 questions presented in a variety of drag-and-drop, drop-down, single-choice, and multi-choice formats.
Try the quiz to check your knowledge!
Clause
Clause vs phrase: a clause has a subject + verb (she runs); a phrase does not (in the morning, running fast). This is the first distinction to make when analysing sentence structure.
A clause is a grammatical unit built around a verb: independent clauses make complete sentences; dependent clauses attach to them as modifiers or complements.
Diagnostic: find the verb. If there's a subject doing or being something → clause. If there's no subject-verb pair → phrase.
Comma
Comma vs semicolon vs period: all three can appear between two complete thoughts. Comma + conjunction (I left, and she stayed). Semicolon alone (I left; she stayed). Period = full stop (I left. She stayed.). Using just a comma between two independent clauses without a conjunction is a comma splice — the most common comma error.
The comma ( , ) separates sentence parts: lists, non-essential info, introductory phrases, and clauses before coordinating conjunctions.
Diagnostic: are both sides complete sentences with no conjunction between them? Don't use a comma alone — upgrade to a semicolon or add a conjunction.
Complex sentence
Complex vs compound sentence: a compound sentence links two equal independent clauses with and/but/or. A complex sentence links an independent clause with a subordinate (dependent) clause — one idea is the main point, the other is background.
A complex sentence = independent clause + dependent clause. The dependent clause adds time (when), reason (because), condition (if), or detail (who/which).
Diagnostic: are both halves able to stand alone? Yes → compound. Can only one stand alone? → complex.
Pronoun
Pronoun vs noun: nouns name explicitly (Sarah, the book). Pronouns substitute and point back (she, it). Pronouns are a closed class (you can't invent new ones easily), while nouns are open (new ones appear constantly). The main complication: pronouns still carry case marking that nouns have lost.
A pronoun replaces a noun or noun phrase. Types: personal, demonstrative, relative, interrogative, reflexive, indefinite.
Diagnostic: every pronoun must have a clear antecedent (the noun it replaces). If the reader can't tell which noun a pronoun refers to → ambiguity error.
Punctuation
Punctuation vs grammar: grammar governs word forms and order. Punctuation governs how you mark the structure on paper. You can have perfect grammar with wrong punctuation (comma splices in otherwise correct sentences), and you can have correct punctuation with broken grammar. They're parallel systems.
Punctuation = the system of marks that make written sentence structure visible: periods, commas, semicolons, colons, apostrophes, dashes, and quotation marks.
Diagnostic: if your grammar is correct but readers misparse your sentences → punctuation problem. If punctuation is fine but word forms/order are wrong → grammar problem.
Relative clause
Restrictive vs non-restrictive: this distinction changes meaning. The students who passed celebrated = only those who passed. The students*, who passed,** celebrated* = all students passed and all celebrated. One missing comma flips the meaning of the entire sentence.
A relative clause = dependent clause modifying a noun. Restrictive (essential, no commas) vs non-restrictive (extra, commas required).
Diagnostic: remove the clause. Does the sentence still identify the right noun? Yes → non-restrictive (add commas). No (now ambiguous) → restrictive (no commas).
B1 | Intermediate
B1 vs B2: B1 handles standard everyday communication and simple opinions. B2 handles abstract topics, sustained arguments, and nuanced register. If you can chat about your life but struggle to debate an issue or write a formal essay, you're B1.
B1 is the intermediate CEFR level: independent handling of familiar topics, second conditional, basic passive, reported speech, and linking words for cause and contrast.
Diagnostic: can you read a newspaper article on a familiar topic and summarise the argument? Comfortably → B2. Struggle with abstractions → still B1.
Medium
Medium vs Easy: Easy has one obviously correct answer and clearly wrong distractors. Medium has one correct answer but plausible distractors — you need to actually know the rule, not just guess from sound.
The Medium tag filters for A2–B1 challenges with realistic difficulty: one rule per question, plausible alternatives, everyday contexts.
Diagnostic: if you're scoring 90%+ on Easy, move here. If you're below 60% on Medium, go back to Easy for that topic. Target 70–80% accuracy for maximum learning.