Auxiliary verb

• ✅ Do you know? — ❌ Know you? (English requires do-support for questions)
• ✅ She has finished. — ❌ She finished has. (auxiliary before main verb)
• ✅ They are leaving. — ❌ They leaving. (progressive needs be)
• ✅ He doesn't smoke. — ❌ He smokes not. (negation needs do)

Auxiliary verbs (be, have, do, and the modals) combine with main verbs to build questions, negatives, tenses, aspects, and passive voice.

Pattern: if you need to ask a question, negate, or stack tense/aspect — you need an auxiliary. The main verb carries meaning; the auxiliary carries grammar.

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.

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 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.

Perfect tense

• ✅ I have lived here for ten years. — present perfect (started past, still true)
• ❌ I live here for ten years. — wrong (simple present can't bridge past→now)
• ✅ She had finished before I arrived. — past perfect (earlier past)
• ✅ They will have left by noon. — future perfect (completed before future point)

The perfect = have + past participle. Connects an action to a reference point in time. Present perfect bridges past→now. Past perfect marks "earlier past." Future perfect marks "done before a future deadline."

Rule: if the action started in the past and is still relevant now → present perfect (have done). If two past events and you need the earlier one → past perfect (had done).

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.