The following outline is provided as an overview of and topical guide to knowledge:

Types of knowledge

By form A priori and a posteriori knowledge – these terms are used with respect to reasoning (epistemology) to distinguish necessary conclusions from first premises. A priori knowledge or justification – knowledge that is independent of experience, as with mathematics, tautologies ("All bachelors are unmarried"), and deduction from pure reason (e.g., ontological proofs). A posteriori knowledge or justification – knowledge dependent on experience or empirical evidence, as with most aspects of science and personal knowledge. Descriptive knowledge – also called declarative knowledge or propositional knowledge, it is the type of knowledge that is, by its very nature, expressed in declarative sentences or indicative propositions (e.g., "Capybaras are rodents", or "It is raining"). This is distinguished from what is commonly known as "know-how" or procedural knowledge (the knowledge of how, and especially how best, to perform some task), and "knowing of", or knowledge by acquaintance (the knowledge of something's existence). Experience – knowledge or mastery of an event or subject gained through involvement in or exposure to it.Compare various contemporary definitions given in the OED (2nd edition, 1989): "[...] 3. The actual observation of facts or events, considered as a source of knowledge.[...] 4. a. The fact of being consciously the subject of a state or condition, or of being consciously affected by an event. [...] b. In religious use: A state of mind or feeling forming part of the inner religious life; the mental history (of a person) with regard to religious emotion. [...] 6. What has been experienced; the events that have taken place within the knowledge of an individual, a community, mankind at large, either during a particular period or generally. [...] 7. a. Knowledge resulting from actual observation or from what one has undergone. [...] 8. The state of having been occupied in any department of study or practice, in affairs generally, or in the intercourse of life; the extent to which, or the length of time during which, one has been so occupied; the aptitudes, skill, judgement, etc. thereby acquired." Empirical evidence – also referred to as empirical data, empirical knowledge, and sense experience, it is a collective term for the knowledge or source of knowledge acquired by means of the senses, particularly by observation and experimentation. After Immanuel Kant, it is common in philosophy to call the knowledge thus gained a posteriori knowledge. This is contrasted with a priori knowledge, the knowledge accessible from pure reason alone. Experiential knowledge – knowledge gained through experience. Explicit knowledge – knowledge that can be readily articulated, codified, accessed and verbalized. It can be easily transmitted to others. Most forms of explicit knowledge can be stored in certain media. The information contained in encyclopedias and textbooks are good examples of explicit knowledge. Extelligence – term coined by Ian Stewart and Jack Cohen in their 1997 book Figments of Reality. They define it as the cultural capital that is available to us in the form of external media (e.g., tribal legends, folklore, nursery rhymes, books, videotapes, CD-ROMs, etc.). Knowledge by acquaintance – according to Bertrand Russell, knowledge by acquaintance is obtained through a direct causal (experience-based) interaction between a person and the object that person is perceiving. Sense-data from that object are the only things that people can ever become acquainted with; they can never truly KNOW the physical object itself. The distinction between "knowledge by acquaintance" and "knowledge by description" was promoted by Russell (notably in his 1905 paper On Denoting). Russell was extremely critical of the equivocal nature of the word "know", and believed that the equivocation arose from a failure to distinguish between the two fundamentally different types of knowledge. Libre knowledge – knowledge released in such a way that users are free to read, listen to, watch, or otherwise experience it; to learn from or with it; to copy, adapt and use it for any purpose; and to share the work (unchanged or modified). Whilst shared tacit knowledge is regarded as implicitly libre, (explicit) libre knowledge is defined as a generalisation of the libre software definition. Procedural knowledge – also known as imperative knowledge, it is the knowledge exercised in the performance of some task. Commonly referred to as "knowing-how" and opposed to "knowing-that" (descriptive knowledge). Tacit knowledge – kind of knowledge that is difficult to transfer to another person by means of writing it down or verbalizing it. For example, that London is in the United Kingdom is a piece of explicit knowledge that can be written down, transmitted, and understood by a recipient. However, the ability to speak a language, knead dough, play a musical instrument or design and use complex equipment requires all sorts of knowledge that is not always known explicitly, even by expert practitioners, and which is difficult or impossible to explicitly transfer to other users. Threshold knowledge

By scope

Common knowledge – knowledge that is known by everyone or nearly everyone, usually with reference to the community in which the term is used. Customer knowledge – knowledge for, about, or from customers. Domain knowledge – valid knowledge used to refer to an area of human endeavour, an autonomous computer activity, or other specialized discipline. Foundational knowledge – the knowledge necessary for understanding or usefully applying further knowledge in a field. General knowledge – information that has been accumulated over time through various mediums. This definition excludes highly specialized learning that can only be obtained with extensive training and information confined to a single medium. General knowledge is an important component of crystallized intelligence and is strongly associated with general intelligence, and with openness to experience. Metaknowledge – knowledge about knowledge. Bibliographies are a form of metaknowledge. Patterns within scientific literature is another.

Self-knowledge – information that an individual draws upon when finding an answer to the question "What am I like?". Traditional knowledge – knowledge systems embedded in the cultural traditions of regional, indigenous, or local communities. Traditional knowledge includes types of knowledge about traditional technologies of subsistence (e.g. tools and techniques for hunting or agriculture), midwifery, ethnobotany and ecological knowledge, traditional medicine, celestial navigation, ethnoastronomy, the climate, and others. These kinds of knowledge, crucial for subsistence and survival, are generally based on accumulations of empirical observation and on interaction with the environment. Traditional ecological knowledge

Qualities of knowledge

Half-life of knowledge

Structure of knowledge

Taxonomies Types of subject taxonomies Document classification Library classification Taxonomy for search engines Specific taxonomies of knowledge Figurative System of Human Knowledge Propædia – first of three parts of the 15th edition of Encyclopædia Britannica, presenting its Outline of Knowledge. Tree of Knowledge System

Types of bodies of recorded knowledge

Academic disciplines – branch of knowledge that is taught and researched as part of higher education. A scholar's discipline is commonly defined and recognized by the university faculties and learned societies to which he or she belongs and the academic journals in which he or she publishes research. However, no formal criteria exist for defining an academic discipline. Body of knowledge (BOK) – specialized term in knowledge representation meaning the set of concepts, terms and activities that make up a professional domain, as defined by the relevant learned society or professional association. Curricula – plural of curriculum, which means the totality of student experiments that occur in the educational process. The term often refers specifically to a planned sequence of instruction, or to a view of planned student's experiences in terms of the educator's or school's instructional goals. Curricula may be tightly standardized, or may include a high level of instructor or learner autonomy. Many countries have national curricula in primary and secondary education, such as the United Kingdom's National Curriculum. Encyclopedias – type of reference work or compendium holding a comprehensive summary of information from either all branches of knowledge or a particular branch of knowledge. Glossary of Library Terms. Riverside City College, Digital Library/Learning Resource Center. Retrieved on: November 17, 2007. Encyclopedias are divided into articles or entries, which are usually accessed alphabetically by article name. Encyclopedia entries are longer and more detailed than those in most dictionaries. Generally speaking, unlike dictionary entries, which focus on linguistic information about words, encyclopedia articles focus on factual information concerning the subject for which the article is named.Béjoint, Henri (2000). Modern Lexicography, pp. 30–31. Oxford University Press. Knowledge base Personal knowledge base Knowledge commons Libraries – a library is a collection of sources of information and similar resources, made accessible to a defined community for reference or borrowing. It provides physical or digital access to material, and may be a physical building or room, or a virtual space, or both."Library ... collection of books, public or private; room or building where these are kept; similar collection of films, records, computer routines, etc. or place where they are kept; series of books issued in similar bindings as set."--Allen, R. E., ed. (1984) The Pocket Oxford Dictionary of Current English. Oxford: Clarendon Press; p. 421 A library's collection can include books, periodicals, newspapers, manuscripts, films, maps, prints, documents, microform, CDs, cassettes, videotapes, DVDs, Blu-ray Discs, e-books, audiobooks, databases, and other formats. Libraries range in size from a few shelves of books to several million items.

Specific bodies of recorded knowledge, by type

Specific BOKs (bodies of knowledge, in the context of the knowledge representation field) Canadian IT Body of Knowledge Civil Engineering Body of Knowledge Common Body of Knowledge Enterprise Architecture Body of Knowledge Geographic Information Science and Technology Body of Knowledge Project Management Body of Knowledge Software Engineering Body of Knowledge Data Management Body of Knowledge Specific encyclopedias Bibliography of encyclopedias List of encyclopedias by branch of knowledge List of encyclopedias by language List of historical encyclopedias List of online encyclopedias Wikipedia – largest encyclopedia in the world. It is a free, web-based, collaborative, multilingual encyclopedia project supported by the non-profit Wikimedia Foundation. Its more than 20 million articles (over 6.89 million in English) have been written collaboratively by volunteers around the world. Almost all of its articles can be edited by anyone with access to the site, and it has about 100,000 regularly active contributors. Specific knowledge bases Knowledge Vault – knowledge base created by Google. As of 2014, it contained 1.6 billion facts which had been collated automatically from the Internet.

Epistemology (philosophy of knowledge)