The number "0.004" is a decimal that represents a value less than one. It can also be expressed as a fraction, specifically 4/1000, which means four parts out of a thousand. In scientific notation, it is written as 4 x 10^-3, indicating that it is a small number. In practical terms, "0.004" can be used in various contexts, such as measuring small quantities. For example, it could represent 4 milliliters in a liter or 4 grams in a kilogram. Understanding this number helps in fields like science, finance, and everyday measurements.