A serial number is a unique identifying number assigned to an individual item for the purpose of tracking and inventory control. However, there are several other terms that can be used instead of "serial number" depending on the particular field or industry. For example, in product manufacturing, a "part number" may be used to identify a specific component. In the field of electronics, a "device number" or "equipment identification number" may be used to identify a piece of equipment. In the context of software, a "license key" or "activation code" may be used to authenticate and activate the software product. Overall, there are many synonyms for "serial number" that can be used depending on the specific context and purpose.