seven is a cardinal number that refers to the quantity of one more than six or the sum of three and four.
simply place it before any noun you're counting. For instance, seven elephants, seven coins, seven days. It's also commonly used to refer to a single group or unit.
1. They had seven apples in the basket.
2. I just bought seven new dresses for the party.
3. The seven-letter word was difficult to guess.
seven is a nice, round number that has a special significance in many religions and cultures, including the seven days of the week, seven chakras, seven colors of the rainbow, etc.