【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.