PART

The concept of "part" is not easy to define though it is intimately connected to the concept "whole". For the formal study of the parthood relation, see mereology.
Other occurrences of the concept:

Contents

In the performing arts

Music

Film, theatre and television

In dance

In mathematics

In engineering

In fashion

In preparing mixtures

In the performing arts

Music

A 'part' is the music played by an individual instrument or voice (or group of identical instruments or voices) within a larger work, such as a melody. It also refers to the printed copy of the music for each instrument, as distinct from the score, which holds the music for all instruments. For example in a string ensemble you would have separate parts for Violin 1, Violin 2, Viola and Cello, even though there might be several of each instrument (and therefore several copies of each part).
A 'part' in great Highland Bagpipe music is a musical sentence. Usually each 'part' consists of four phrases, either one or two bars long. Several sentences combine to produce a paragraph or complete work or tune.
See also: singer, register, ensemble, polyphony, counterpoint.

Film, theatre and television

In film, theatre and television, a ''part'' is an actor's role.

In dance

A 'part' is a dancer's role, particularly in a major work such as a classical ballet.

In mathematics

A 'part' is any geometric object such as a point, line, arc, circle, polygon, polyhedron, or polytope that can be joined together to form a whole. It may also be defined as a bounded region in the plane, for two-dimensional geometry, or as a bounded region in space, for three-dimensional geometry.
There are two kinds of parts: complex and simple. Complex parts can be dissected into simple parts, and simple parts cannot be dissected further.
"Imaginary part" is a common but somewhat odd term, because although it provides part of the information about a complex number, it is not a part in the normal sense.

In engineering

A 'part' is a component used in a higher-level mechanical or electrical assembly. Examples of parts are screws, transistors and other electronic components, a specially shaped piece of metal required by the mechanism of a specific model of video cassette recorder, and a myriad other examples. Parts required to replace broken parts in existing equipment are called spare parts or just spares.

In fashion

The 'part' or 'parting' of a person's hair is the "watershed" line at which the hair is parted, or divided. Some people part their hair in the middle (a "center part," following the natural part of the hair), and some part their hair at one side or the other. See also: hairstyle.

In preparing mixtures

It is customary to specify an undefined amount of a mixture in either parts or percentages. For example the cocktail known as a Martini is described as being made with 5 parts of gin to 1 of vermouth.