If you know one word, you are about to know 100. The fancy word for this is NUANCE. The longer explanation is synonyms are words that mean sort of the same thing, not exactly the same thing. That’s where nuance comes in, what different that keeps synonyms from meaning exactly the same thing. It can be hard to tell- but easy to feel.
Do you want people to think you are beautiful? cute? handsome? pretty?
There you go. The words all suggest the same thing, but for me I’d rather people said I was beautiful instead of pretty. It just feels better.

There is no set answer on the limits of meaning for words, at one point it is all up to you. While we can’t have fixed answers, we can respect the range of meaning it is possible for words to hold. One fun way to check what other people think a word means is through social media hashtags, especially on sites like Instagram. You get an instant picture dictionary.
I have some activity sheets to help you think this through too. One looks like a Venn diagram, so we can draw out the places where words overlap in a common meaning while also showing where they differ. EAT and DRINK both mean CONSUME. One is consuming solid foods, the other liquid.

Another way to do this is to write sentences using each of the synonyms while trying to be sure each sentence conveys the nuance in meaning for each word.

Let’s look at BIG, MAJOR and IMPORTANT.
Tokyo is a BIG city, almost 14 million people live there.
Tokyo is BIG in the sense of population. The number of people who live in Tokyo is a very BIG number.
Tokyo is a MAJOR city with two international airports.
Tokyo is a BIG transportation hub. Even if the population of Tokyo was small, it would still be a MAJOR city because of the airports.
Tokyo is an IMPORTANT city, it is the capital of Japan.
Even if Tokyo was very small and had no airports it would still be an important city because it is the capital of Japan.
Interesting side note, a very small city in the United States is Montpelier, the capital of Vermont. Montpelier is important for being the capital of Vermont even though the population of Montpelier is less than 10,000 people. Montpelier doesn’t even have a McDonald’s. That may make it an especially important city.

Another way of understanding synonyms is thinking about the very different ways people talk about the same thing. Think about your hand. How would you describe your hand? Do you think a doctor would use the same words to talk about your hand? I know I would need to bring a dictionary along with me or ask a lot of questions because my doctor is going to use a lot of unfamiliar words.

As we learn synonyms and appreciate the nuance they bring to our conversations and our thinking we will get a better and richer understanding of English.