Which term describes a device functioning without human intervention?

The term that best describes a device functioning without human intervention is "automatic." Automatic devices are designed to operate independently, often utilizing sensors or programmed instructions to perform their functions. This capability allows them to respond to changing conditions or inputs without requiring a person to actively control them.

For instance, many modern home appliances, such as washing machines and thermostats, operate automatically by following pre-set programs or reacting to environmental changes, thus providing convenience and efficiency in various tasks.

While "manual" refers to devices that require human operation, "electronic" denotes devices that use electronic components but does not necessarily imply they operate autonomously. "Programmable" suggests that a device can be set to run certain tasks based on user-defined instructions, but it doesn’t inherently indicate automation if it still requires manual initiation. Hence, "automatic" is the most accurate term to denote devices that work without direct human control.