A more thorough explanation:

Definition: Trade usage refers to a customary and uniform practice that is well-known in a specific profession or business. It is a practice or method of dealing that has such regularity of observance in a region, vocation, or trade that it justifies an expectation that it will be observed in a given transaction.

Examples: A common example of trade usage is the practice of tipping in the service industry. It is customary to tip waiters, bartenders, and hairdressers in the United States, and it is expected that customers will follow this practice. Another example is the use of industry-specific jargon or terminology. For instance, doctors use medical terms that are not commonly understood by the general public, but are well-known and expected within the medical profession.

Explanation: Trade usage is a well-established practice that is widely recognized and followed within a particular industry or profession. It is not a legal rule, but rather a customary or habitual practice that is relied upon by those who are conversant in, or connected with, a trade or business. The examples illustrate how trade usage is a common and expected practice within certain industries, and how it can vary from one profession to another.