A list is a set of discrete items of information collected and set forth in some format for utility, entertainment, or other purposes. A list may be memorialized in any number of ways, including existing only in the mind of the list-maker, but lists are frequently written down on paper, or maintained electronically. Lists are "most frequently a tool", and "one does not read but only uses a list: one looks up the relevant information in it, but usually does not need to deal with it as a whole".
An outline, also called a hierarchical outline, is a list arranged to show hierarchical relationships and is a type of tree structure. An outline is used to present the main points (in sentences) or topics (terms) of a given subject. Each item in an outline may be divided into additional sub-items. If an organizational level in an outline is to be sub-divided, it shall have at least two subcategories, although one subcategory is acceptable on the third and fourth levels, as advised by major style manuals in current use. An outline may be used as a drafting tool of a document, or as a summary of the content of a document or of the knowledge in an entire field. It is not to be confused with the general context of the term "outline", which is a summary or overview of a subject presented verbally or written in prose (for example, The Outline of History is not an outline of the type presented below). The outlines described in this article are lists, and come in several varieties.
A sentence outline is a tool for composing a document, such as an essay, a paper, a book, or even an encyclopedia. It is a list used to organize the facts or points to be covered, and their order of presentation, by section. Topic outlines list the subtopics of a subject, arranged in levels, and while they can be used to plan a composition, they are most often used as a summary, such as in the form of a table of contents or the topic list in a college course's syllabus.
A bill of materials or product structure (sometimes bill of material, BOM or associated list) is a list of the raw materials, sub-assemblies, intermediate assemblies, sub-components, parts, and the quantities of each needed to manufacture an end product. A BOM may be used for communication between manufacturing partners or confined to a single manufacturing plant. A bill of materials is often tied to a production order whose issuance may generate reservations for components in the bill of materials that are in stock and requisitions for components that are not in stock.
The first hierarchical databases were developed for automating bills of materials for manufacturing organizations in the early 1960s. At present, this BOM is used as a database to identify the many parts and their codes in automobile manufacturing companies.
An enumeration is a complete, ordered listing of all the items in a collection. The term is commonly used in mathematics and computer science to refer to a listing of all of the elements of a set. The precise requirements for an enumeration (for example, whether the set must be finite, or whether the list is allowed to contain repetitions) depend on the discipline of study and the context of a given problem.
Some sets can be enumerated by means of a natural ordering (such as 1, 2, 3, 4, ... for the set of positive integers), but in other cases it may be necessary to impose a (perhaps arbitrary) ordering. In some contexts, such as enumerative combinatorics, the term enumeration is used more in the sense of counting – with emphasis on determination of the number of elements that a set contains, rather than the production of an explicit listing of those elements.
A ranking is a relationship between a set of items, often recorded in a list, such that, for any two items, the first is either "ranked higher than", "ranked lower than", or "ranked equal to" the second. In mathematics, this is known as a weak order or total preorder of objects. It is not necessarily a total order of objects because two different objects can have the same ranking. The rankings themselves are totally ordered. For example, materials are totally preordered by hardness, while degrees of hardness are totally ordered. If two items are the same in rank it is considered a tie.
By reducing detailed measures to a sequence of ordinal numbers, rankings make it possible to evaluate complex information according to certain criteria. Thus, for example, an Internet search engine may rank the pages it finds according to an estimation of their relevance, making it possible for the user quickly to select the pages they are likely to want to see.
A shopping list is a list of items needed to be purchased by a shopper. Consumers often compile a shopping list of groceries to purchase on the next visit to the grocery store (a grocery list). There are surviving examples of Roman and Bible-era shopping lists.
The shopping list itself may be simply a scrap piece of paper or something more elaborate. There are pads with magnets for keeping an incremental list available at the home, typically on the refrigerator, but any magnetic clip with scraps of paper can be used to achieve the same result. There is even a specific device that dispenses a strip of paper from a roll for use in a shopping list. Some shopping carts come with a small clipboard to fit shopping lists on.
A short list or shortlist is a list of candidates for a job, prize, award, political position, etc., that has been reduced from a longer list of candidates (sometimes via intermediate lists known as "long lists"). The length of short lists varies according to the context. A candidate on a short list may or may not receive the award or position.