You are correct that sector is the answer most fitting. Section = a part of a whole, sometimes made physically separate (or conceptually separate) without great thought or reason - or with a system such as a grid, rather than through consideration of separate functions. Sector = a part set aside for a specific purpose or function (this is what you are referring too.) A sector may or may not be in a grid system, but if it is, gridded sectors may have unique functions. A sector can have physical boundaries or it can be conceptually set apart. Conceptually separate: Within the whole, there are those that work with a specific, separate element of the business. area = a space or conceptual space, being thought of as separate (not necessarily set apart in any literal, physical way) Physical area examples: section of a building or land Conceptual areas: business type or education category Part = a piece of a larger whole: the term does not specify importance to the whole. Some parts are quite important while some are less important. Every section, piece and sector can be thought of as a part. An area is not a part. Parts can be thought of both separate yet connectable. Areas tend not to be separated physically.

1) a part is a region or area (part of my town) but also - one of the pieces, periods, things, etc. that together with others forms the whole of something (ex.: Some parts of the film are nice) 1) a section is one of the parts into which something is divided (the financial section of a newspaper); 2) a sector can be a part of an area or of a large group of people or a part of the business activity of a country (the public/private sector); 3) an area (a region) is a part of a town, a country or the world;