Typically in contrast to Essential Functions, the term refers to those functions constituting or part of a job that are accessorial, extra, incidental, nonessential and/or peripheral, whereas Essential Functions are those that are critical, crucial, fundamental, primary, indispensable and integral.
Apart from being necessary in job descriptions generally, the distinction is especially pertinent to the Americans with Disabilities Act which lays down decision-making to be along the lines of the distinction. Marginal functions are ‘marginal’ only with respect to the job it is said to be marginal to, not marginal per se.
For instance, for a job that requires operating a machine, any task related to the aesthetic upkeep of the machine is a marginal function.
Both essential functions as well as marginal functions are a part of a job description.
A few factors to consider when determining a function as essential or marginal:
1. Tasks within the job
2. Affect of functions on other employees and their jobs