Sometimes when we are reading we come across new words that we don't understand.
There may be somebody around who we can ask, or we can use a dictionary, but we can also use context. This means looking at the rest of the sentence to see if it helps us understand the new word.
Jack was so hungry that he didn't leave a single particle of the cake on his plate.
You may not be familiar with the word particle, but from the context you can guess that it means a very small piece of something.