Gerund

Gerund vs infinitive: the biggest source of errors for non-native speakers. Some verbs take only gerund (enjoy reading ✅), some only infinitive (want to read ✅), some take both with different meanings (stop reading ≠ stop to read). There's no logical rule — these must be learned by verb.

A gerund is the -ing verb form used as a noun. After prepositions = always gerund. After certain verbs (enjoy, avoid, finish) = always gerund. After to (preposition, not infinitive marker) = gerund (I look forward to seeing you).

Diagnostic: can you replace the -ing word with "it" or "something"? I enjoy it → yes, it's acting as a noun = gerund.

Participle

Present participle vs gerund: both are -ing forms, but a participle acts as an adjective/adverb (the running water, She sat reading), while a gerund acts as a noun (Running is fun). Same form, different grammatical job.

A participle = verb form used as modifier or in compound tenses. Present (-ing): progressive + adjective. Past (-ed/irregular): perfect + passive + adjective.

Diagnostic: is the -ing word describing a noun or modifying a verb? → participle. Is it being a noun (subject, object)? → gerund.

B2 | Upper Intermediate

B2 vs C1: B2 means effective communication on complex topics with some effort. C1 means effortless fluency with precise register control. If you can argue a point but still reach for words and make structural slips under pressure, you're B2.

B2 is the upper-intermediate CEFR level: mixed conditionals, complex passives, reported speech with backshift, participle clauses, and sustained written argument.

Diagnostic: does your writing read as "competent non-native" or "could be native"? The former → B2. The latter → C1.

Hard

Hard vs Medium: Medium tests one rule with realistic distractors. Hard tests interacting rules, edge cases, or context-dependent answers where multiple options seem correct until you think deeply. If you're scoring 80%+ on Medium, try Hard to find your real gaps.

The Hard tag filters for B2+ challenges with layered difficulty: rule interactions, subtle distractors, and contexts that demand genuine grammatical reasoning.

Diagnostic: if Hard questions feel impossible, drop to Medium and master the individual rules first. Hard assumes you already know each rule — it tests whether you can apply them together.