It’s nice to have something physical, but I will say that learning every word in our language is impossible. It’s got more words than almost any language, and you’ll never even need to use any of them. I have a rule when it comes to learning Polish: never learn a word I wouldn’t use in English. What you should do is ensure you have all the most common vocabulary down, as you appear to, and then learn every new word you come across and are unfamiliar with. That way, you’ll ensure you are not learning words you will never need to use, wasting valuable time that could be spend on more productive pursuits. You ought to simply use the dictionary as a reference when you encounter such unknown words, unless you are content to sell it and simply use online resources.

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I think Cambridge is better for learners. It's been a while since university years when I had them both at hand, but as far as I remember, Cambridge would ofer definitions and sentence examples (obviously helpful to learners), while Oxford would offer definitions and origin of the words (more useful for people who study language history and linguistics). I think in a way it was more of a conversational practical English vs technical and all-encompassing English (i.e. Cambridge vs Oxford). As one who likes to be specific with my words, I used to prefer Oxford, but I think Cambridge is easier to use. More on reddit.com

Collins Dictionary. Not only could you find the word meanings, but also the synonyms and how people would normally construct sentence with the word. More on reddit.com

I recommend Cambridge Dictionary, it provides simple, short and easy to undestand definitions and it also explains a lot of idioms.

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