The term "normal unit operation" can be replaced with a variety of synonyms, depending on the context and industry. For example, in the medical field, it might be more appropriate to use "standard procedure" or "routine protocol." In manufacturing or engineering, "regular operation" or "standard practice" could be used. Other possible synonyms include "typical process," "usual function," or "ordinary task." Ultimately, the choice of synonym will depend on the specific language and jargon used within the field. Regardless of the phrase used, it refers to the regular and expected procedures or processes that are part of a larger system or operation.