Familiar words are words that you are used to using in your speech and writing. It is also likely that you understand their meaning. Unfamiliar words are the opposite; words you do not understand or...
As I walked down the street, I spotted a familiar looking man who was staring suspiciously at a cat. I am familiar with this word. How familiar are those two?
The word "familiar" is made from the basic English word "family". The word family is derived from the Latin familia, meaning household, or often family.