In engineering, a function is interpreted as a specific process, action or task that a system is able to perform.
[1] In the lifecycle of engineering projects, there are usually distinguished subsequently: Requirements and Functional specification documents.
For example a calculator capable of the basic mathematical operations of addition, subtraction, multiplication, and division, would be called a "four-function" model; when other operations are added, for example for scientific, financial, or statistical calculations, advertisers speak of "57 scientific functions", etc.
A wristwatch with stopwatch and timer facilities would similarly claim a specified number of functions.
To maximise the claim, trivial operations which do not significantly enhance the functionality of a product may be counted.