The neighbor _________________________ called the police was wearing a superhero onesie.
The suspect's parrot, which is known for screaming at midnight, woke up the entire building.
The neighbor who called the police was wearing a superhero onesie.
Use which (not that) for non-defining relative clauses—the ones separated by commas that add extra, non-essential information about a thing or animal.
Use who as the subject pronoun for people in defining relative clauses. (Whom is used for objects, and which is used for things).
Relative clause
- ✅ The man who called is my uncle. — restrictive (essential: which man?)
- ✅ My uncle, who lives in Paris, called. — non-restrictive (extra info, commas)
- ❌ My uncle that lives in Paris — wrong (that can't introduce non-restrictive)
- ✅ The book that I read = The book I read — restrictive (pronoun optional)
Relative clauses modify nouns using who/whom/whose/which/that or where/when/why. Restrictive = essential, no commas, that OK. Non-restrictive = extra, needs commas, uses which/who (never that).
Rule: if you can remove the clause and still know which noun is meant → non-restrictive (commas). If removing it makes the noun ambiguous → restrictive (no commas).
Pronoun
- ✅ between you and me — ❌ between you and I (objective case after preposition)
- ✅ its colour — ❌ it's colour (it's = it is)
- ✅ She did it herself. — reflexive pronoun
- ✅ The person who called… — relative pronoun
Pronouns replace nouns: personal (I/me/my), demonstrative (this/that), relative (who/which/that), interrogative (who?/what?), reflexive (myself), indefinite (everyone/nobody). They carry case that nouns have lost.
Trap: pronouns are where English case still matters: I vs me, who vs whom, its vs it's. Get these wrong and it's instantly noticeable.
Comma
- ✅ apples, pears, and figs — list separator
- ✅ My brother, a doctor, called. — non-essential info set off by commas
- ✅ I went home, and she stayed. — comma before conjunction joining two clauses
- ❌ I went home and she stayed. — missing comma (two independent clauses need one before and)
The comma ( , ) separates elements within a sentence: list items, non-essential phrases, introductory words, and clauses joined by coordinating conjunctions.
Rule: if two independent clauses are joined by and/but/or, put a comma before the conjunction. If it's just a compound verb (same subject), no comma.
Clause
- I missed the bus. — ✅ independent clause (stands alone)
- Because I overslept. — ❌ fragment (dependent clause, can't stand alone)
- Because I overslept, I missed the bus. — ✅ dependent + independent = complete sentence
- I missed the bus, and I was late. — ✅ two independent clauses joined by and
A clause is a unit built around a verb with a subject. Independent = can stand alone. Dependent = needs an independent clause to complete it.
Test: does the group of words have a subject + verb AND can it be a sentence on its own? Yes → independent clause. Has a subject + verb but feels incomplete → dependent clause.
Punctuation
- Period (.) — ends statements
- Comma (,) — separates within sentences
- Semicolon (;) — links related independent clauses
- Colon (:) — introduces what follows
- Question mark (?) — ends direct questions
- Apostrophe (') — possession + contractions
Punctuation marks signal sentence structure to the reader: where thoughts end, how they connect, what's quoted, and what belongs to whom. ~12 marks, each with specific rules.
Key insight: punctuation isn't about pauses in speech. It's about grammatical structure. Learn the structure, and the punctuation follows.
B1 | Intermediate
- ✅ If I had more time, I would travel more. — second conditional
- ✅ The bridge was built in 1920. — passive voice
- ✅ She said she was tired. — reported speech with backshift
- ✅ Although it rained, we enjoyed the trip. — complex sentence with concession
These are B1 patterns — the CEFR intermediate level. At B1 you link ideas, use passive voice, handle reported speech, and manage second conditional — enough for travel, work basics, and everyday independence.
Marker: if you can explain why something happened and follow a news story, you're B1.
Medium
- If I were you, I would apologise. — one rule (second conditional), but distractors like was tempt you
- Answers require active thought, not instant pattern recognition
- Vocabulary and context are realistic, not artificially simplified
- Usually tests one rule, but the wrong answers are plausible
Medium marks middle-difficulty challenges: A2–B1, one rule tested, but with realistic distractors that require genuine understanding.
Use "Medium" when Easy feels too obvious but Hard feels overwhelming. This is where most productive learning happens — the sweet spot of difficulty.