co
English · B2 · (no translation)
CO is a dangerous gas you cannot see or smell.
co in real context
co is a B2-level word in English meaning "" in this vocabulary set. Every word on LangOria comes with a real example sentence, so you meet co the way native speakers actually use it — not as an isolated dictionary entry, but inside a living English sentence.
The example sentence for co is: "CO is a dangerous gas you cannot see or smell." (). Learning co through example sentences helps you internalize English word order and collocations, so co is ready the first time you actually need it.
Add co to your B2 spaced-repetition review and it will resurface right before you are about to forget it — tomorrow, in three days, in a week. Combined with the rest of the English B2 vocabulary set, a daily 45–65 minute loop is the fastest proven path from first exposure to confident, natural use of co.
About English B2
B2 is the upper-intermediate tier of CEFR. At B2 you can interact with a degree of fluency and spontaneity that makes regular interaction with native speakers quite possible, produce clear detailed text on a wide range of subjects, and explain a viewpoint on a topical issue. B2 is the level most universities and employers mean when they ask for 'fluent English'.
How to learn English B2
B2 takes 3-6 months on top of B1. Continue reviewing A1-B1 (5-minute daily) and add 50-100 new B2 words per week. Read English news and long-form journalism, listen to English podcasts at natural speed, and try writing 500-1000 word essays for correction. By the end of B2 you should be able to debate any familiar topic in English and read most non-technical English text without a dictionary.
Common questions about co in English
What level is co in English?
In LangOria's English deck, co sits at the B2 level of the language's recognized ability ladder (CEFR for most languages, JLPT for Japanese, HSK for Chinese). At this level you learn co alongside the highest-frequency words you actually need.
How do I memorize co?
Rote repetition rarely sticks on its own. Learn co inside its example sentence, say it out loud, and let spaced repetition bring it back at the right moments. The 45–65-minute daily loop is usually enough to anchor co in long-term memory.
Where does the example for co come from?
Every word — including co — carries a real example drawn from the community-built Tatoeba sentence corpus: sentences written by native speakers, not synthetic textbook filler. That context is what makes co memorable.
What should I learn after co?
Cover the remaining words at the B2 level, then move up. LangOria schedules spaced reviews and frequency-ordered decks, so co reinforces the rest of your B2 English vocabulary instead of standing alone.