What is the square root of 81?

The square root of a number is a value that, when multiplied by itself, gives the original number. In this case, you are looking for a number that, when squared, equals 81.

Since (9 \times 9) equals 81, the square root of 81 is indeed 9. This makes it the correct choice, as it perfectly fulfills the condition of the square root definition. Understanding that squaring a number is the opposite operation of finding a square root is key to solving such questions effectively.

In addition, considering the other options, they do not yield 81 when squared: (7 \times 7) equals 49, (8 \times 8) equals 64, and (10 \times 10) equals 100. This highlights why 9 is the only correct answer.