Any type of book, website, or application which provides information on what a word is understood to mean is relevant to everything I read or write.
When I am reading something and see a new word, I often use a dictionary to get a general idea of what it means. When I am writing, I still search for certain words so that I can see if there is a synonym which is more commonly understood by people. This is extremely relevant to communication.
For example, the word “mad” can be used to describe either anger or insanity. These are not the same thing. While there is a chance that a person who is angry can become insane, there is also the possibility that a person is angry because they are sane enough to be angry about a real problem. It is more relevant to use either “angry” or “insane” instead of “mad” so that people can understand what is intended.
Another example is the word “mature”. Normally this word is used to describe a movie, TV show, video game, or book full of people who are saying and doing all kinds of irrelevant things which I would consider to be very “immature”. One synonym for “mature” is “adult”. Because both of these words are assumed to have something to do with a persons age, I avoid them since I have already explained why age is irrelevant.