It’s hard to believe, but we didn’t always have the ability to reach for a dictionary to look up a word to see what it meant. Even when dictionaries were around, there were no guarantees that you could find the words, understand the definition, or that the information given was even correct!
Today, there are many dictionaries to choose from. Which one you use depends on, well, you. You may prefer learner dictionaries that give definitions in simple words that are easy to understand. I really like using a learner dictionary to teach ESL. However, more advanced students may require more advanced and specific definitions that include the etymology, or origin and history, of a word. The etymology of a word may not seem that important, but it really is. It gives us insight into where the word came from, how its usage has changed and often can provide a nuance, or shade, to the exact meaning. Synonyms and antonyms are often useful in helping to better understand a word or for vocabulary expansion. Spelling dictionaries provide an easy-to-find list of words broken down into syllables without long definitions and other distracting text, for quick reference. Finally, technical dictionaries cater to specific fields of study and provide definitions and usages based on very specific and detailed uses of technical words. An example of one of these would be a medical dictionary.
Some dictionaries also cater to American English over British English, and this depends on your preference. Dictionaries, like the OED, will include words that are archaic, or out of common use. This might be extremely useful for some readers, but confusing for others.
Technology has, of course, changed the way we use dictionaries. We used to have to first hunt down a big volume and then flip through the pages to find a word. Now, voice activated artificial intelligence technology let’s me find out just about anything I need to know with a simple voice command. “Siri, what does anthropomorphic mean?”
Technology has, however, inadvertently brought us back to the problem of knowing for sure that the information we are receiving is accurate. While we still can trust well-known sources, sometimes we find that we are getting information from a website that lacks credibility. I have googled a word and found myself on a forum or other site that uses popular opinion or comments to provide answers to questions, without any guarantee of the accuracy of. After all, anyone can set up a website or write a blog. This reminds me a bit of OED’s method of gathering definitions.
These are the dictionaries I use in my personal study, as well as English teaching and consulting:
My favorite American English dictionary: https://www.merriam-webster.com/
My favorite British dictionary: http://www.oed.com/
Honorable mention British dictionary: http://dictionary.cambridge.org/us
My favorite American learner’s: http://learnersdictionary.com/
My favorite British learner’s: http://www.ldoceonline.com/
My favorite etymology site: http://etymonline.com/