The symbol "<" means?

The symbol "<" is used in mathematical and scientific contexts to denote that one value is smaller than another. When you see "<," it indicates that the value on the left side of the symbol is less than the value on the right side. For instance, if you have the expression "3 < 5," it asserts that 3 is indeed less than 5.

Understanding this symbol is essential in various fields, including mathematics, physics, and engineering, where comparing quantities and determining their relationships is critical. This foundational concept aids in making calculations and assessments in water treatment processes, where determining acceptable levels of various substances often involves comparisons of numerical values.

The other options do not reflect the correct meaning of the symbol. "More than" would be represented by ">", "approximately" is often denoted by "≈", and "rounder than" is not a standard mathematical term or symbol at all.