The unit of measurement used to determine the diameter of a human cell is typically the micrometer (µm).

Here's why:

* Human cells are very small: Most human cells are microscopic, meaning they are too small to be seen with the naked eye.

* Micrometers are a suitable scale: A micrometer is one millionth of a meter (1 µm = 10⁻⁶ m). This unit provides a convenient scale for measuring the tiny dimensions of cells.

* Other units can be used, but less common: While other units like nanometers (nm) might be used for specific cellular components, micrometers are the standard for measuring the overall size of human cells.

So, when you see the diameter of a human cell described as 10 µm, for example, you know it's a very small object, about 1/100th the width of a human hair.