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.

Conditional sentence

• ✅ If you heat ice, it melts. — zero conditional (always true)
• ✅ If it rains, I'll take an umbrella. — first conditional (real future)
• ✅ If I had wings, I would fly. — second conditional (unreal present)
• ✅ If I had left earlier, I would have caught the train. — third conditional (unreal past)

Conditional sentences pair an if-clause with a consequence. Five patterns (zero through mixed) each combine specific tenses to express different levels of reality and time.

Pattern: the tense in the if-clause is always one step "back" from what you'd expect — past for present hypotheticals, past perfect for past hypotheticals.

Inversion

• ✅ Has Sam read it? — question inversion (basic)
• ✅ Rarely have I seen such talent. — fronted negative (advanced)
• ✅ Not only does she sing, she also writes. — correlative inversion
• ✅ Had I known, I would have acted. — inverted conditional (no if)

Inversion = subject and auxiliary swap places. Basic: all English questions. Advanced: fronted negatives/restrictives (Rarely…, Not only…, Never…) and formal conditionals without if.

Pattern: put a negative/restrictive adverb at the front → invert subject and auxiliary. This is a C1+ rhetorical device for emphasis.

Modal verb

• ✅ She can swim. — ❌ She can to swim. (modal + bare infinitive, no to)
• ✅ You must leave now. — strong obligation
• ✅ It might rain. — possibility (~50%)
• ✅ He should apologise. — advice/recommendation

Modal verbs (can, could, may, might, must, shall, should, will, would) are auxiliaries expressing ability, permission, possibility, obligation, or speculation. Always + bare infinitive. Never inflected (she can, not she cans).

Rule: modals never take to after them, never add -s for third person, and can't combine directly (must can ❌ — use must be able to).

Negation

• ✅ I don't see anything. — ❌ I don't see nothing. (double negative in standard English)
• ✅ She never goes out. — never already negates (no doesn't needed)
• ✅ He doesn't like coffee. — do-support for negation
• ✅ Nobody came. — negative subject (no auxiliary needed)

Negation uses not after an auxiliary/modal, or do-support when there's no auxiliary. One negative per clause in standard English — never, nobody, nothing already negate without adding not.

Rule: one negative element per clause. I don't see anything or I see nothing — never both together in standard English.

Past tense

• I walked home. — simple past (completed action)
• I was walking when it rained. — past progressive (in progress)
• I had already left when she arrived. — past perfect (earlier past)
• I had been waiting for an hour. — past perfect progressive (duration up to a past point)

Four past tense forms: simple past (done), past progressive (was happening), past perfect (had already happened), past perfect progressive (had been happening). Each encodes different timing relative to other past events.

Pattern: simple past = the story's main timeline. Past progressive = background action. Past perfect = flashback to something even earlier.

Subjunctive mood

• ✅ If I were you… — past subjunctive (not was)
• ✅ I suggest that he go. — present subjunctive (not goes)
• ✅ It's important that she be present. — present subjunctive
• ❌ If I was you… — common in speech, avoided in formal writing

The subjunctive uses bare-infinitive forms (go, be) after verbs of demand/suggestion, and were (not was) in unreal/hypothetical conditions. Two contexts: that-clauses (I insist that he leave) and if-clauses (If she were here).

Rule: after suggest/recommend/demand/insist that… → use base form. In if + unreal condition → use were for all persons.

Verb

• walk → walk / walks / walked / walked / walking (5 forms, regular)
• go → go / goes / went / gone / going (5 forms, irregular)
• be → am/is/are/was/were/be/being/been (8 forms)
• can → can / could (modal: only 2 forms, no -s, no -ing)

A verb is the one word class every English sentence requires. Carries tense (when), aspect (duration), mood (attitude), and voice (active/passive). Regular verbs add -ed; ~200 irregular verbs have unpredictable past forms.

Key insight: fix your verbs and most grammar problems disappear. Wrong tense, wrong agreement, wrong form — verb errors account for the majority of grammatical mistakes.

Verb mood

• Indicative: She goes every day. — stating fact
• Imperative: Go now. — giving command
• Subjunctive: I suggest she go. — hypothetical/recommendation
• Conditional: She would go if asked. — dependent on condition

Verb mood marks the speaker's attitude: indicative (fact), imperative (command), subjunctive (unreal/recommended), conditional (would/could). English barely marks mood morphologically — mostly through auxiliaries and word order.

Rule: stating a fact? → indicative. Giving a command? → imperative. Imagining/recommending? → subjunctive or conditional. The mood determines which verb forms and auxiliaries you use.

Verb tense

Verb tense = time (past/present/future) × aspect (simple/progressive/perfect) = 12 forms. Each slot has a specific job — not just "when" but "how the action relates to its time frame."

Key insight: most learners don't need all 12 at once. Simple covers 80% of communication. Add perfect and progressive as needed.

Progressive tense

• ✅ I am working in London. — temporary, happening now
• ✅ I work in London. — permanent/habitual (simple)
• ❌ I am knowing the answer. — stative verb, can't be progressive
• ✅ She was reading when I arrived. — past progressive (in progress at that moment)

The progressive = be + -ing. Marks actions as ongoing, temporary, or in-progress at a reference time. NOT used with stative verbs (know, believe, own, want, like) unless meaning shifts.

Rule: is the action temporary/in-progress right now? → progressive. Is it a permanent fact, habit, or schedule? → simple. Is it a stative verb? → almost never progressive.

Simple tense

• ✅ I go to work every day. — present simple (habit)
• ✅ She went home yesterday. — past simple (completed action)
• ✅ I will call you later. — future simple (promise/decision)
• ✅ Water boils at 100°C. — present simple (general truth)

The simple aspect is the default, unmarked verb form. Present simple = habits, facts, schedules. Past simple = completed actions. Future simple = predictions, promises, decisions. No auxiliary needed (except will for future and do for questions/negatives).

Rule: if the action is a fact, habit, completed event, or scheduled future — and you don't need to emphasise it being in-progress or connected to now → simple tense.

Word order

• ✅ She (S) eats (V) cake (O). — standard SVO
• ❌ Cake eats she. — SOV (not English)
• ✅ a lovely little old rectangular green French silver whittling knife — adjective order (opinion→size→age→shape→colour→origin→material→purpose)
• ✅ Never have I seen… — inversion after negative adverb

English word order = SVO (subject-verb-object) as default. Adjectives follow a fixed sequence (opinion→size→age→shape→colour→origin→material). Adverb placement varies by type. Deviations signal questions, emphasis, or literary style.

Rule: when in doubt, default to SVO. English position = meaning. Move a word and you change the grammar or the emphasis.

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.

B2 | Upper Intermediate

• ✅ If I had studied harder, I would have passed. — third conditional
• ✅ The report is being reviewed by the committee. — passive progressive
• ✅ Having finished the exam, she left. — participle clause
• ✅ He denied having taken the money. — complex verb pattern

These are B2 patterns — the CEFR upper-intermediate level. At B2 you handle mixed conditionals, all passive forms, participle clauses, and can argue a point clearly. This is the level most universities and employers require.

Marker: if you can write a structured essay and debate an abstract topic, you're B2.

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.