What is the primary characteristic of a saturated fatty acid?

The primary characteristic of a saturated fatty acid is that it contains no double bonds. This structural feature means that every carbon atom in the fatty acid chain is fully "saturated" with hydrogen atoms, allowing it to hold the maximum number of hydrogen atoms possible. As a result, saturated fatty acids typically have straight chains that can pack closely together, contributing to their solid state at room temperature in many cases.

While it's true that saturated fatty acids are often solid at room temperature, this is more of a physical property that results from their structure rather than a defining characteristic. It's also important to distinguish saturated fatty acids from unsaturated ones, which contain one or more double bonds in their chains, affecting their shape and behavior at different temperatures.