The correct answers are:
- The alien has eight tentacles. It is quite friendly, though.
- Although the alien has eight tentacles, it is quite friendly.
Though can be used as an adverb at the very end of a sentence to show contrast. "Although" cannot be used this way.
When using although as a conjunction, it introduces a dependent clause and is separated from the main clause by a comma. We never use a semicolon followed by "although."
Finally, using a comma before however to connect two complete sentences creates a "comma splice," which is grammatically incorrect. It needs a period or a semicolon!
Adverb
Adverb vs adjective: adjectives describe things; adverbs describe actions, qualities, or degrees. The mix-up usually happens after action verbs — she sings beautiful (wrong) vs she sings beautifully (right).
An adverb modifies a verb, adjective, or another adverb: incredibly fast, she spoke softly, we go often.
Diagnostic: ask what word is this describing? If it's a verb (an action) → adverb. If it's a noun (a thing) → adjective. Exception: linking verbs (be, seem, taste) take adjectives, not adverbs.
Conjunction
Coordinating vs subordinating conjunction: coordinating (and, but, or) joins two elements of equal rank — clause + clause, noun + noun. Subordinating (because, although, if) makes one clause depend on the other. The test: remove the conjunction. If both halves still feel complete → coordinating. If one half collapses → subordinating.
Conjunctions are connecting words for clauses, phrases, and words. The choice between coordinating and subordinating determines whether you're building a compound or complex sentence.
Diagnostic: does the conjunction create a dependent clause? Yes → subordinating. Does it link equals? → coordinating.
Compound sentence
Compound vs complex sentence: compound = two equal independent clauses (I left, and she stayed). Complex = one main clause + one dependent clause (I left because I was tired). The key: in a compound sentence, both halves can stand alone.
A compound sentence links independent clauses with coordinating conjunctions (and, but, or, so, yet) or a semicolon.
Diagnostic: split at the conjunction. Can both halves be their own sentences? Yes → compound. Is one half a fragment without the other? → complex.
Punctuation
Punctuation vs grammar: grammar governs word forms and order. Punctuation governs how you mark the structure on paper. You can have perfect grammar with wrong punctuation (comma splices in otherwise correct sentences), and you can have correct punctuation with broken grammar. They're parallel systems.
Punctuation = the system of marks that make written sentence structure visible: periods, commas, semicolons, colons, apostrophes, dashes, and quotation marks.
Diagnostic: if your grammar is correct but readers misparse your sentences → punctuation problem. If punctuation is fine but word forms/order are wrong → grammar problem.
Clause
Clause vs phrase: a clause has a subject + verb (she runs); a phrase does not (in the morning, running fast). This is the first distinction to make when analysing sentence structure.
A clause is a grammatical unit built around a verb: independent clauses make complete sentences; dependent clauses attach to them as modifiers or complements.
Diagnostic: find the verb. If there's a subject doing or being something → clause. If there's no subject-verb pair → phrase.
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.
Medium
Medium vs Easy: Easy has one obviously correct answer and clearly wrong distractors. Medium has one correct answer but plausible distractors — you need to actually know the rule, not just guess from sound.
The Medium tag filters for A2–B1 challenges with realistic difficulty: one rule per question, plausible alternatives, everyday contexts.
Diagnostic: if you're scoring 90%+ on Easy, move here. If you're below 60% on Medium, go back to Easy for that topic. Target 70–80% accuracy for maximum learning.