They say that most English speakers use 20,000 words to get by in their lives, which is a pretty big number, but it is a drop in the bucket compared to the massive number of words that exist in the language. There are even new words added every year and definitions changed based on the use of language in our lives. English is constantly evolving, but having a large vocabulary can help you express yourself the way that you mean without mistakes and miscommunications. It is also a big help when it comes to the SAT, which requires a lot of vocabulary knowledge. To digress about French, I think it is really interesting the different words that they have for relationships that describe different levels of intimacy. In English, we basically just have single, married, and it’s complicated. With a large vocabulary, you can express everything that you want to.
Going with that vocabulary is pronunciation because reading words does not always mean that you are going to pronounce them correctly. Every single person on the planet that speaks English has mispronounced a word that they have only read before because they never bothered to learn the proper pronunciation. I remember mine in 4th grade as dachshund, which I pronounced with a lot of Germanic throat noises instead of realizing it was the little wiener dog. A funny one in college was when a friend pronounced tentacle like debacle, which coincidentally I have also heard mispronounced like tentacle in the past. Getting the words right just takes hearing the right ones and practicing to make sure that you are not doing it wrong. You could learn the pronunciation symbols from the dictionary and learn that way, but I will only allow the computer to pronounce it for me because I need to hear it pronounced. My favorite football team drafted a guy named Oshane Ximines this year and I decided that it would be a smart move to avoid his last name until I heard it pronounced.
Now that we have gone over some of the challenges of vocabulary and pronunciation, we should talk a little about what you can do to improve on your skills. For vocab, you have probably heard of the note card method in the past, which is a tried and true method for studying that many students use. On one side of the card, write the word. On the other side of the card, write the definition. Try going back and forth between guessing the definition from the word and guessing the word from the definition. That is probably the simplest and cheapest way to learn words, but it does not do too much to provide context. In terms of individual words, knowing them does not do much good if you do not know how to use them in a sentence. One way to expand your vocabulary and learn about the word in context is to read a lot. You can see how the word fits in a sentence and get a better sense of how you can use it in the future.