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.

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.

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.

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).

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.