Which of the following best defines a "device"?

The term "device" is best defined as a tool or piece of equipment because it encompasses a wide range of physical instruments designed for a specific function or use. Devices can include anything from simple tools like a hammer to complex machines like computers, making this definition broad and applicable across various contexts. This understanding aligns with common usage in fields such as engineering, technology, and healthcare, where "device" often refers to any functional equipment used to perform tasks, solve problems, or enhance capabilities.

In contrast, while a manual tool specifically refers to hand-operated equipment, it does not capture the full spectrum of what can be considered a device. A software application, although it can be part of a device's functionality, is not itself a physical tool or equipment. Theory or concepts lack the tangible, functional characteristics that define a device, further solidifying that "tool or piece of equipment" is the most accurate definition.