Part, portion, piece, detail, member, division, section, segment, sector, fraction, fragment, parcel are comparable when they mean something which is less than the whole but which actually is or is considered as if apart from the rest of the whole.
Part is the most comprehensive of these terms; it may be used in place of any of the succeeding words in this group or even in place of such words as element, component , or constituent (see ELEMENT ).
Portion, although it denotes a part of a whole, does not always presuppose a compact or integral whole; it may suggest a whole that comprises all of an existing or a possible stock or store without any connotation of its assemblage.
But portion (see also FATE ) is preferred to part when there is the intent to imply determination of amount or quantity or assignment or allotment, especially of a share.
Piece applies to a separate or detached part or portion of a whole; thus, a piece of bread is a part of a larger whole such as a loaf; a piece of cloth may be a length cut from a bolt, a smaller length left after the larger part of that piece has been used, or a bit that serves as a swatch or sample.
But piece so stresses the implication of independence that the term may come close to item and then is often applied to a thing that is relatively complete in itself, and has reference to a whole only as it presupposes a mass from which it was taken, a collection of similar or related things, especially as produced by one person, one machine, or one factory.
Detail (see also ITEM ) applies to a part chiefly when the presupposed whole is a plan or design, or represents the working out of a plan or design; in this sense the term is used largely in the arts of painting, sculpture, and architecture, and often denotes a small but important part or feature.
Member applies to a part that constitutes one of the units of which a body (as a human or animal body, a social or legislative body, or a constructed or manufactured body) is comprised; the term, though it usually implies close association with the body under consideration, also usually implies separability of the unit in thought or in fact.
Division and section apply to a distinct, often a detached, part formed by or as if by cutting or dividing. The terms are often used interchangeably, but division is usually applied to larger parts than is section; thus, one would refer to the divisions of modern languages and of political sciences of a college but to the several sections into which a large class of students taking a course is divided.
Except in technical use, the terms carry no explicit suggestions as to size or extent; division, however, is more often used abstractly than section, which tends to be applied to a conspicuously distinct part (as of a writing, a people, a country, a territory, or a city).
Segment is often preferred to section for a part cut off by natural lines of cleavage or necessitated by the nature of the thing's construction or design. In mathematical use segment is distinguished from sector in that segment refers to any part of a plane or solid figure cut off from the whole by a line or plane while sector refers to any part of a circle bounded by an arc and two radii.
In more general use sector applies to a section that roughly corresponds to a mathematical sector; thus, a sector assigned to a commander of a division in war has arbitrary bounds on sides and rear but a front that is as extensive as the range of its guns.
Fraction and fragment both apply to a part that is disconnected from a whole, especially by breaking; but fraction, probably by its confusion with the arithmetical sense of that word, often suggests a negligible part and fragment applies to a random bit and especially to one of the pieces left after most of the whole has been eaten, used, worn away, or lost.
Parcel (see also BUNDLE ) is used chiefly in law with reference to land and in such idiomatic phrases as part and parcel ; in all its uses it carries an underlying notion of a part having a firm and unbreakable connection with the whole to which it belongs.