Which term describes a unit that is defined by a combination of SI base units?

• A. Derived unit
• B. Fundamental unit
• C. Atomic unit
• D. Standard unit

Answer: (A)

Verified step by step guidance

1. Understand that SI units are categorized into base units and derived units. Base units are the fundamental units defined independently, such as meter (m), kilogram (kg), second (s), etc.
2. Recognize that a derived unit is formed by combining these base units through multiplication or division according to physical relationships. For example, velocity is meters per second (m/s), which combines the base units meter and second.
3. Identify that the question asks for the term describing a unit defined by a combination of SI base units, which matches the definition of a derived unit.
4. Recall that fundamental units are the base units themselves, atomic units are related to atomic-scale measurements, and standard units refer generally to accepted units but not specifically to combinations of base units.
5. Conclude that the correct term for a unit defined by a combination of SI base units is 'Derived unit'.