What term describes the number of separations during a month, including voluntary and involuntary terminations, expressed as a percentage?

The term that accurately describes the number of separations during a month, encompassing both voluntary and involuntary terminations expressed as a percentage, is "Turnover Rate." This metric is crucial for organizations as it provides insight into employee retention and workforce stability. A high turnover rate can indicate potential issues within the workplace, such as low employee satisfaction, challenges in management, or insufficient compensation, prompting management to investigate and make necessary changes.

In contrast, retention rate is concerned with the percentage of employees remaining with the organization over a certain period; employment rate typically refers to the percentage of the workforce that is employed versus unemployed in a certain area; and separation rate, although similar, may not specifically factor in the total workforce and could have different definitions depending on the context. Hence, "Turnover Rate" is the most accurate and specific term for the scenario described in the question.