The fraction 0.9 represents a decimal number that is equivalent to nine-tenths. In fractional terms, it can be expressed as 9/10, meaning that if you divide something into ten equal parts, nine of those parts would make up 0.9. This value is commonly used in mathematics and everyday situations, such as measuring or calculating percentages. In the context of real numbers, 0.9 is a repeating decimal, which can also be represented as 0.999.... This notation indicates that the digit 9 continues indefinitely. Interestingly, 0.9 and 0.999... are mathematically equal, demonstrating an important concept in number theory.