A diagram is a symbolic representation of
information Information can be thought of as the resolution of uncertainty; it answers the question of "What an entity is" and thus defines both its essence and the nature of its characteristics. The concept of ''information'' has different meanings in d ...

using visualization techniques. Diagrams have been used since ancient times on walls of caves, but became more prevalent during the Enlightenment. Sometimes, the technique uses a three-dimensional visualization which is then projected onto a two-dimensional surface. The word '' graph'' is sometimes used as a
synonym A synonym is a word, morpheme, or phrase that means exactly or nearly the same as another word, morpheme, or phrase in the same language. For example, the words ''begin'', ''start'', ''commence'', and ''initiate'' are all synonyms of one another ...
for diagram.


The term "diagram" in its commonly used sense can have a general or specific meaning: * ''visual information device'' : Like the term " illustration", "diagram" is used as a collective term standing for the whole class of technical genres, including graphs, technical drawings and tables. * ''specific kind of visual display'' : This is the genre that shows qualitative data with shapes that are connected by lines, arrows, or other visual links. In science the term is used in both ways. For example, Anderson (1997) stated more generally: "diagrams are pictorial, yet abstract, representations of information, and maps, line graphs, bar charts,
engineering Engineering is the use of scientific method, scientific principles to design and build machines, structures, and other items, including bridges, tunnels, roads, vehicles, and buildings. The discipline of engineering encompasses a broad rang ...
blueprints, and
architect An architect is a person who plans, designs and oversees the construction of buildings. To practice architecture means to provide services in connection with the design of buildings and the space within the site surrounding the buildings that ha ...

s' sketches are all examples of diagrams, whereas photographs and video are not".Michael Anderson (1997). "Introduction to Diagrammatic Reasoning," at ''cs.hartford.edu.'' Retrieved 21 July 2008. On the other hand, Lowe (1993) defined diagrams as specifically "abstract graphic portrayals of the subject matter they represent". In the specific sense diagrams and charts contrast with computer graphics, technical illustrations, infographics, maps, and technical drawings, by showing "abstract rather than literal translation, literal representations of information". The essence of a diagram can be seen as: * a ''form'' of visual Content format, formatting devices * a ''display'' that does not show quantitative data (numerical data), but rather relationships and abstract information * with ''building blocks'' such as geometrical shapes connected by wikt:line, lines, arrows, or other visual links. Or in Hall's (1996) words "diagrams are simplified figures, caricatures in a way, intended to convey essential meaning".Bert S. Hall (1996). "The Didactic and the Elegant: Some Thoughts on Scientific and Technological Illustrations in the Middle Ages and Renaissance". in: B. Braigie (ed.) ''Picturing knowledge: historical and philosophical problems concerning the use of art in science''. Toronto: University of Toronto Press. p.9 These simplified figures are often based on a set of rules. The basic shape according to White (1984) can be characterized in terms of "elegance, clarity, ease, pattern, simplicity, and validity". Elegance is basically determined by whether or not the diagram is "the simplest and most fitting solution to a problem".

Gallery of diagram types

There are at least the following types of diagrams: * Logical or conceptual diagrams, which take a collection of items and relationships between them, and express them by giving each item a 2D position, while the relationships are expressed as connections between the items or overlaps between the items, for example: * Quantitative diagrams, which display a relationship between two variables that take either Discrete mathematics, discrete or a continuous function, continuous ranges of values; for example: * Schematics and other types of diagrams, for example: Many of these types of diagrams are commonly generated using diagramming software such as Microsoft Visio, Visio and Gliffy. Thousands of diagram techniques exist. Some more examples follow Diagrams may also be classified according to use or purpose, for example, explanatory and/or how to diagrams.

Specific diagram types

;A *Activity diagram used in Unified Modeling Language, UML 6/9 and SysML ;B *Bachman diagram *Booch method, Booch – used in software engineering *Block diagram *Block definition diagram (BDD) used in SysML ;C *Carroll diagram *Cartogram *Catalytic cycle *Computer network diagram *Chemical equation *Arrow pushing, Curly arrow diagram *Diagram (category theory), Category theory diagrams *Cause-and-effect diagram *Chord diagram *Circuit diagram *Class diagram – from Unified Modeling Language, UML 1/9 *Cobweb diagram *Communication diagram, Collaboration diagram – from Unified Modeling Language, UML 2.0 *Communication diagram – from Unified Modeling Language, UML 2.0 *Commutative diagram *Comparison diagram *Component diagram – from Unified Modeling Language, UML 3/9 *Composite structure diagram – from Unified Modeling Language, UML 2.0 *Concept map *Constellation diagram *Context diagram *Control flow diagram *Contour diagram *Cordier diagram *Cross functional flowchart ;D *Data model diagram *Data flow diagram *Data structure diagram *Dendrogram *Dependency diagram *Deployment diagram – from Unified Modeling Language, UML 9/9 *Dynkin diagram *Dot and cross diagram *Double bubble map – used in education *DRAKON, Drakon-chart ;E *Entity-relationship diagram (ERD) *Event-driven process chain *Euler diagram *Eye diagram – a diagram of a received telecommunications signal *Exploded-view drawing *Express-G *Extended functional flow block diagram (EFFBD) ;F *Family tree *Feynman diagram *Flow chart *Flow process chart *Flow diagram *Fusion diagram *Free body diagram ;G *Gantt chart – shows the timing of tasks or activities (used in project management) *Grotrian diagram *Goodman diagram – shows the fatigue (material), fatigue data (example: for a wind turbine blades) ;H *Hasse diagram *HIPO diagram ;I *Internal block diagram (IBD) used in SysML *IDEF0 *IDEF1 (entity relations) *Interaction overview diagram – from Unified Modeling Language, UML *Ishikawa diagram ;J *Jackson Structured Programming, Jackson diagram *Jones diagram ;K *Karnaugh map *Kinematic diagram *Knot diagram ;L *Ladder logic, Ladder diagram *Levi graph *Line of balance *Link grammar, Link grammar diagram ;M *Martin ERD *Message sequence chart *Mind map – used for learning, brainstorming, memory, visual thinking and problem solving *Minkowski diagram, Minkowski spacetime diagram *Molecular orbital diagram *Motion diagram ;N *N2 diagram, N2 *Nassi–Shneiderman diagram or structogram – a representation for structured programming *Nomogram *Network diagram ;O *Object diagram – from Unified Modeling Language, UML 2/9 *Organigram *Onion model, Onion diagram – also known as "stacked Venn diagram" ;P *Package diagram from Unified Modeling Language, UML 4/9 and SysML *Parametric diagram from SysML *PERT *Petri net – shows the structure of a distributed system as a directed bipartite graph with annotations *Phylogenetic tree - represents a phylogeny (evolutionary relationships among groups of organisms) *Piping and instrumentation diagram (P&ID) *Phase diagram used to present solid/liquid/gas information *Plant diagram *Pressure volume diagram used to analyse engines *Pourbaix diagram *Process flow diagram or PFD – used in chemical engineering *Program structure diagram ;R *Radar chart *Radial diagram *Requirement diagram Used in SysML *Rich picture *Randolph diagram, R-diagram *Routing diagram ;S *Sankey diagram – represents material, energy or cost flows with quantity proportional arrows in a process network *Sentence diagram – represents the grammar, grammatical structure of a natural language sentence *Sequence diagram from Unified Modeling Language, UML 8/9 and SysML *Specification and Design Language, SDL/GR diagram – specification and description Language. SDL is a formal language used in computer science. *Smith chart *Radar chart, Spider chart *Spray diagram *SSADM – structured systems analysis and design methodology (used in software engineering) *Star chart/Celestial sphere *State diagram are used for state machines in software engineering from Unified Modeling Language, UML 7/9 *Swim lane *Syntax diagram used in software engineering to represent a context-free grammar *Systems Biology Graphical Notation – a graphical notation used in diagrams of biochemical and cellular processes studied in systems biology *System context diagram *System structure *Systematic layout planning ;T *Timing diagram: digital timing diagram *Timing diagram: Unified Modeling Language, UML 2.0 *TQM diagram *Treemapping, Treemap ;U *Unified Modeling Language#Diagrams, UML diagram – Unified Modeling Language (used in software engineering) *Use case, Use case diagram – from Unified Modeling Language, UML 5/9 and SysML ;V *Value stream mapping *Venn diagram *Voronoi diagram ;W *Warnier-Orr *Wedge-dash diagram *Williot diagram ;Y *Yourdon-Coad – see Edward Yourdon, used in software engineering

See also

* Chart * Table (information) * Diagrammatic reasoning * Diagrammatology * List of graphical methods * Mathematical diagram * Plot (graphics) * commons:Specific diagram types – gallery of many diagram types. * commons:Commons:Diagram resources


Further reading

* * Michael Anderson, Peter Cheng, Volker Haarslev (Eds.) (2000). ''Theory and Application of Diagrams: First International Conference, Diagrams 2000''. Edinburgh, Scotland, UK, September 1–3, 2000. Proceedings. * Garcia, M. (ed.), (2012) ''The Diagrams of Architecture''. Wiley. Chichester. {{Visualization Infographics Diagrams, Modeling languages