Please keep an eye on the target's apartment from the van. If you catch no article sight of anyone leaving through the back door, notify me immediately. We cannot afford to be left in the dark about his movements tonight.
keep an eye on: This idiom means "to watch someone or something carefully" and uses the indefinite article "an" (because "eye" starts with a vowel sound).
catch sight of: This fixed phrase means "to suddenly notice or see someone/something" and requires zero article.
in the dark: When used metaphorically to mean "uninformed" or "ignorant about something," this idiom always takes the definite article "the".
Article
If you speak a language without articles — Russian, Japanese, Polish, Korean, Mandarin — articles in English are probably the single most stubborn topic you face. The rules feel small but the wrong choice (I went to the home instead of I went home) immediately marks you as non-native. Mastering articles is the highest-leverage move you can make for sounding natural.
Articles are a small group of determinatives — a, an, the, plus the zero article (no article at all) — that signal whether a noun is specific or general. The choice depends on the listener's knowledge, the noun type, and idiomatic context.
Determiner
If you speak a language without articles or demonstratives — Mandarin, Russian, Polish, Japanese, Korean — determiners are likely the most stubborn topic in your English. The rules feel small but the wrong choice (I went to home instead of I went home) immediately marks you as non-native. Mastering determiners is the highest-leverage move you can make for sounding natural.
A determiner comes before a noun to clarify which one, how many, or whose. Categories include articles (a/the), demonstratives (this/that), possessives (my/your), and quantifiers (some/many).
Idiom
If you've ever heard a native speaker say that's a piece of cake and wondered what cake had to do with anything — you've met your first idiom. English films, songs, and casual chat are full of these fixed expressions, and missing them leaves the meaning slightly off-kilter. Learning idioms in chunks is the fastest way to stop sounding overly formal.
An idiom is a fixed phrase whose meaning isn't built from its individual words. Kick the bucket (= to die), spill the beans (= reveal a secret), break a leg (= good luck). They have to be memorised as whole units; word-by-word translation almost always misleads.
Collocations
If your English vocabulary is large but your speech still sounds slightly off — do a mistake, powerful coffee, high winds blew strongly — you've hit the collocation problem. Each word is correct in isolation, but native speakers don't pair them that way. Fixing it isn't about more vocabulary; it's about learning words in their natural company.
Collocations are word combinations that habitually occur together: make a decision, strong coffee, heavy rain, highly unlikely. The grammar permits other pairings, but fluent English consistently chooses one over the rest. They're the connective tissue of natural-sounding language.
B2 | Upper Intermediate
If a university admissions team or visa office has ever asked you for an English test score, B2 is probably the level they had in mind. It's the threshold where your English stops being a constraint and starts being a tool — and the line between B1 and B2 is often the line between "stuck in beginner classes" and "ready to study or work in English."
B2 is the upper-intermediate level in the CEFR framework, demanding flexible control of mixed conditionals, passive voice across tenses, reported speech with backshifting, and participle clauses.
Difficulty: Hard
If easy and medium questions are clicking but you still feel exposed in real conversation or formal writing, you've outgrown the basics. Hard material is where the gaps you didn't know you had show up: the distractor that "sounds right", the rule that interacts with another rule, the case where context changes the answer. It's where genuine fluency is built.
The Hard difficulty tag marks upper-intermediate to advanced challenges — typically B2 and above. Interacting rules, edge cases, plausible distractors, and contexts that require genuine understanding rather than surface pattern-matching.