Is there a kind of "official" dictionary for the English language?
Solution 1:
English does not have an official dictionary. However, I think the three most respected ones in the United States are Merriam-Webester, Oxford's, and Collins. You have to buy an Oxford dictionary, so that's not going to work very well for you. The Merriam-Webster's website is found at http://www.merriam-webster.com, and the Collins one can be found at http://www.collinsdictionary.com/dictionary/american-cobuild-learners. My personal favorite is http://www.dictionary.reference.com. While not as official, it is trusted by my English teacher.
And if I have learned anything in my Spanish class as school, do not trust google translate. Otherwise this is liable to happen.
Solution 2:
There is no official dictionary or even consistent worldwide rules of spelling and grammar. The only real rule in English is to write so that you can be understood. The best way to do that is to use a dictionary that was created as geographically close to your audience as possible. Even if it is a free online dictionary.
Solution 3:
https://en.oxforddictionaries.com/definition/study
http://www.oxfordlearnersdictionaries.com/us/definition/english/
OED links above are free, online, and quite respected and considered as good authority in general.
Oxford produces many dictionaries, differing in how many words are defined and whom the primary target audience is. Here's a couple of online free OED access URLs to get you started. Look for the small, light blue icon shaped like the flared bell of a horn's mouth with arcs depicting sound waves.
When that audio icon is part of a word's listing, just click on it to hear the word pronounced. (Note - I don't know if the audio icon appears only on a computer-accessed page, or if it is or isn't also provided if access is permitted using a smartphone or tablet. I mention that because sometimes the mobile versions of apps don't have quite the same properties as computer-format ones.) Audio is seldom provided using the US dictionary option.
Use the default that simply says Dictionary. That one is for British and world English usage which is often different than Americanized English. Or in the Oxford Advanced Learner's Dictionary, the British English and the North American English pronunciations are often provided on the same screen.
For those looking for a fairly authoritative, respected dictionary, those Oxford dictionaries linked above may be helpful.