utility

In computers, a utility is a small program that provides an addition to the capabilities provided by the operating system. In some usages, a utility is a special and nonessential part of the operating system. The print "utility" that comes with the operating system is an example. It's not absolutely required to run programs and, if it didn't come with the operating system, you could perhaps add it. In other usages, a utility is an application that is very specialized and relatively limited in capability. A good example is a search-and-replace utility. Some operating systems provide a limited capability to do a search-and-replace for given character strings. You can add a much more capable search-and-replace utility that runs as an application program. However, compared to a word processor, a search-and-replace utility has limited capability.