I have a lot of dictionaries but itīs a hell when you don't find something easily.
I mean expression , special uses, etc.

I would like a categorizing of what kind of use has the word . For example if itīs from the core of the language or not. I would like something similar to a scale (more useful , less useful)

There are a lot of dictionary online for free , but maybe i īm losing a lot without paying a service:

For example:

Oxford Dictionaries (US)
Oxford University Press

I am afraid of being a scam the first one.

If the money itīs the problem what dictionary service do you buy? , or what dictionary are the best offline (doesn't matter the OS).

I think the more important its how actual the dictionary is, because the language change too much.

(in bilingual version for spanish too)

Thank you for your opinions.