Assembly - a design composed of elements folded from several sheets of paper which hold together in an integrated manner without the use of glue.

Back-coating - a process by which two different materials (such as metal-foil and tissue-paper) are laminated together to form a single foldable sheet.

Base - originally a configuration of folds which offers opportunities for further development in many different ways but more recently also used to mean a preliminary fold which contains the correct number of manipulable points for the intended design.

Bleached paper - homogeneous paper produced by bleaching the fibres during the manufacturing process.

Blintz - to fold all four corners of a square into the centre, thus reducing the paper to half its original size.

Box-pleating - a technique in which the model is in effect produced by pleating and collapsing a long square-section tube of paper.

Bronze rectangle - the paperfolding term for the rectangle which has edges in the proportion of 1:sqrt3.

Bronze triangle - a term for the triangle made by cutting a bronze rectangle in half diagonally which has edges in the proportion of 1:2:sqrt3 and internal angles of 30/60/90 degrees.

Building with Butterflies - descriptive of a delicate style of modular origami in which the individual modules do not possess integral tabs and pockets. Also the title of a book by David Mitchell in which many of the modules are of this kind.

Centre-pocket module - a module which has a slit across the central region of the module into which the tabs of two other modules may be inserted from different directions. The well-known Sonobe module is a module of this type.

Collapse - a complex fold in which a grid of previously established intersecting creases are used simultaneously.

Complex fold - a fold which flattens to form more than one crease or makes use of more than one crease that has been established earlier in the folding sequence.

Compound module - a module which is itself made out of several other modules.

Contrast module - a module folded in such a way that the part of the module that remains visible after the design is assembled is formed partly from one surface of the paper and partly from the other.

Contrast pattern - a pattern formed by combining contrast modules. Contrast patterns may be single-colour or multi-colour.

Corner-pocket module - a module in which some of the corners have been turned inside out to form pockets into which the tabs of other modules (formed from corners that have not been turned inside out) can be inserted.

Crease - Generally, a permanent line of weakness established by completely flattening the axis of a fold, or the act of creating such a weakness. Occasionally, a similar line of weakness created by scoring the paper.

Differentiated paper - paper in which the two surfaces are easily distinguishable in terms of colour, pattern or texture.

Dimpled - description used of a polyhedral model made in such a way that the flat faces of the standard mathematical form are replaced by inverted pyramids. (See also faceted.)

Double bronze rectangle - the rectangle formed by joining two bronze rectangles together long edge to long edge or by cutting a bronze rectangle in half across its shorter width.

Duo - differentiated paper manufactured for folding whose surfaces have been differentiated. Duo paper may be either plain or patterned. The surfaces of plain duo are each printed a different plain colour. One surface of patterned duo is printed with a pattern and the other with a plain colour.

Drawing with paper - a paperfolding technique in which the two distinctly different surfaces of a sheet of differentiated paper are used to create a simple picture on one surface of the model.

Dry tensioning - a technique for inducing curves in paper through tension created by carefully placed creases (as opposed to curves created by wet-folding).

Dyed paper - homogeneous paper produced by dying the fibres during the manufacturing process.

Eccentric - a term used to describe modular cubes in which the pattern on every face is different from the pattern on every other face.

Edge module - a module which forms one edge of a polyhedral model. Because there are many types of edge module the term is insufficient in itself and should be used in conjunction with clarifying terms like 'open-frame', 'split-face' etc. A full classification of edge modules has not been made. See also face module and vertex module.

Edge-pocket module - a module which has pockets along two (or more) edges into which the tabs of other modules may be inserted.

Ethics - self-imposed design standards within which individual paperfolding designers may (or may not) choose to work, such as, for instance, whether to allow the use of cuts, glue or decoration etc and whether to work only from squares, regular polygons, convex shapes etc.

Exploratory paperfolding - investigating the possibilities inherent in the process of paperfolding by structured trial and error.

Face module - a module which forms one complete face of a polyhedral model. The module for Paul Jackson's cube is a classic example of a face module. See also edge module and vertex module.

Faceted - a term used to mean that the flat faces of a polyhedral form have been replaced by inverted pyramids. A skeletal model can be considered to be a faceted form. (See also dimpled.)

Flat origami - paperfolding in which each fold is made through 180 degrees and flattened to create a crease. This kind of origami is particularly amenable to mathematical analysis.

FIT - abbreviation standing for Five Intersecting Tetrahedra, the name of a modular design by the American paperfolder Tom Hull.

Foil - paper backed with metal foil.

Fold - the result of, or the process of, introducing a change of direction into the previously flat plane of the paper.

Fold-line - a broken line used in origami diagrams to show where the crease formed by flattening a fold will form. A dashed line is used to represent a valley fold and a dashed and dotted line to represent a mountain fold.

Folded edge - a double-layer edge created by flattening a fold to form a crease.

Folding geometry - a system of angles which work in combination with each other during the process of folding paper, for instance, 90/45/22.5 or 120/60/30 etc

Found paper - paper which has been manufactured and marketed for purposes other than paperfolding eg writing paper, newsprint, advertising flyers etc, but which is subsequently purchased or collected to be used for folding.

Glossary - a list of questionable definitions.

Hexoid - a three-dimensional modular assembly made from six identical modules.

Homogeneous paper - paper in which the two surfaces are identical or closely similar in colour, pattern and texture. (The two surfaces of machine manufactured papers can always be distinguished by close examination.)

Inverted - turned inside out or inwards.

Irogami - differentiated paper manufactured for folding which is white on one surface and printed a single plain colour on the other. This kind of paper is also sometimes referred to as 'kami' (the general Japanese word for paper) or simply as 'origami paper', but both of these terms are confusing and irogami should be preferred. Irogami literally means 'shaded or coloured paper'. The term 'patterned irogami' can be used to refer to paper which is white on one surface and printed with a pattern on the other.

Iso-area folding - a style of paperfolding and virtual paperfolding invented by Toshihazu Kawasaki in which the aim is to produce a model (such as a flat pattern or polyhedral form) whose final structure possesses iso-area symmetry.

Iso-area model - a model or virtual model which possesses iso-area symmetry.

Iso-area symmetry - rotational inverse symmetry in which similar folds or virtual folds are made in alternative directions after a specified degree of rotation has been applied.

Judgement fold - a fold for which exact location points do not exist, and which must therefore be made by eye alone.

Kirigami - paperfolding in which cuts are used as an aid to the development of points and detail.

Kusudama - Japanese word for a hanging ball of herbs or flowers. In origami a term used for multipiece or modular balls of origami flowers. Sometimes used (incorrectly) to refer to any ball-like modular origami assembly.

Limping seagulls - a term used to refer to the 'M' configuration of the Sonobe module.

Location points - the location points are the two parts of the paper that must be brought together in order that the crease produced by flattening the fold will form in the correct place.

Macromodular origami - a development of modular origami in which complete modular assemblies are combined into integrated second-generation structures either with or without the use of joining pieces.

Macromodule - a complete modular assembly that can be used to build a secong generation structure.

Manoeuvre - a complex fold.

Minimalist origami - a type of representational origami in which the subject is suggested using the smallest possible number of folds.

Model - any paperfold at any stage in the folding process or after the folding has been completed. The use of the word model to describe a paperfold does not imply that the design is representational.

Modular origami - a two stage paperfolding technique which uses multiple sheets of paper. In the first stage each sheet of paper is folded into a module. In the second stage the modules are assembled into an integrated flat shape or three-dimensional structure.

The two stages of modular origami are are not always as separate as the wording of this definition implies. Sometimes the folding of the modules continues after they have been assembled, the classic example being Philip Shen's Omega Star.

Origami using multiple sheets which do not interlock (or which interlock but are folded into completely dissimilar units) is called multi-piece origami.

In Japan, modular origami is known as yunnito (unit) origami.

Module - The word 'module' was originally an architectural term for a standard unit of measurement - all modules being exactly the same - but it is now in common use in a wider sense .... the lunar module, for instance, was simply a separate unit of the Apollo spacecraft. In origami however, the word 'module' still implies that the units are either all identical (usually) or occur in sets of complementary units making up identical sub-assemblies (more rarely) or at the very least are similar in that they begin from the same basic folds.

Some paperfolders use the word 'unit' instead of 'module'. They mean the same and are completely interchangeable.

Mountain and valley folds - poetic terms invented by the Japanese paperfolder Akira Yoshizawa to describe the direction of movement of a fold in relation to the plane of the model, in much the same way as the terms clockwise and anticlockwise describe the direction of movement around a circle. Mountain and valley folds are identical except in relation to the observer. In general a fold in which the moving part of the paper travels through an arc towards the folder is described as a valley fold and one in which the moving part of the paper travels through an arc away from the folder is described as a mountain fold. The terms are inherently confusing and their use should be avoided wherever possible.

Movement-arrow - a curved arrow used in origami diagrams to show the direction in which a fold is to be made.

MRC - abbreviation standing for Magic Rose Cube, a modular design in which a cube opens up into a rose, designed by the American paperfolder Valerie Vann.

Multi-colour pattern - a pattern formed by combining plain modules which have been folded from several different colours or patterns of paper.

Multi-colour contrast pattern - a pattern formed by combining contrast modules folded from several different colours or patterns of paper.

Multi-piece origami - origami using multiple sheets of paper. Modular origami can be viewed as a sub-set of multi-piece origami.

Naive origami - a class of representational multiple sheet origami invented by the British paperfolder David Mitchell which must conform to six simple rules.

Nolids - solids of no volume which are composed of planes lonking the edges of the polyhedron with the centre of symmetry. In origami nolids are a type of planar design.

One-fold origami - a technique invented by the British paperfolder Paul Jackson in which curves are induced in the paper by first making, then breaking a single crease. The technique is misnamed to the extent that the 'break' is in fact a very short second crease.

OFTC - abbreviation for Origami for the Connoisseur, the English title of a book wriiten by Kunihiko Kasahara and Toshie Takahama.

Open-frame polyhedra - modular polyhedra in which the centre of the faces are missing. Also known as outline polyhedra.

Organic origami - a technique popularised by the French paperfolder Vincent Floderer in which paper is first crumpled then stretched and moulded into organic shapes.

Origami - a Japanese word meaning 'folding paper' adopted into English and other languages without any change of meaning. Synonymous with paperfolding.

Outline polyhedra - modular polyhedra in which the centre of the faces are missing. Also known as open-frame polyhedra.

Outline edge module - an edge module which forms part of an outline or open-frame polyhedral model.

Plain module - a module folded in such a way that the part of the module that remains visible after the design is assembled is formed from just one surface of the paper.

Platinum rectangles - a term proposed by David Mitchell for the twin rectangles which contain the golden-proportion triangles arranged apex to apex and which are therefore of particular use in obtaining elegant designs based on 108 / 72 / 36 degree folding geometry.

Pre-creasing - Specifically, the technique of creating a crease at an early stage in a folding sequence which will not be used in the structure of the model until a later stage is reached. Generally, a folding technique in which a series of intersecting creases are created individually then used in combination.

Pure origami - a style of origami in which the only material used is paper (no foil etc) and the only process used is folding (no cuts, no glue, no decoration).

Pureland origami - a folding style invented by the British paperfolder John Smith which attempts to explore what can be achieved if the range of permissible technique is limited to basic mountain and valley folds made and used individually.

RAT - abbreviation standing for 'right about there' - a way of referring to the positioning of a judgement fold.

Raw edge - a single layer edge, originally one of the outside edges of the unfolded paper.

Semi-naive origami - a type of naive origami in which rules 3 or 5 are not adhered to.

Silver rectangle - the rectangle which has sides in the proportion of 1:sqrt2. This rectangle is also sometimes known as the true rectangle or as DIN size paper.

Silver triangle - the right-angle isosceles triangle, which shares with the silver rectangle the property that it can be continuously bisected into self-similar shapes.

Silverhedra - polyhedra whose faces are all silver triangles.

Simple fold - a fold which flattens to form a single crease or makes use of a single crease that has been established earlier in the folding sequence. See complex fold.

Single-colour contrast pattern - a pattern formed by combining contrast modules folded from just one colour or pattern of paper.

Sink - a complex fold in which a corner of the model is turned inside out to become a pocket. Sinks may be either open or closed. An open sink is one in which the layers of the paper can be opened to allow the sink to be achieved in a structured manner. A closed sink is one where the layers of the paper cannot be opened and the sink must be performed in an ad hoc manner. Closed sinks can often be turned into open sinks by a careful restructuring of the layers.

Skeletal polyhedra - modular models of nolids (solids of no volume) in which the planes of the nolid are represented in paper.

Soft fold - a fold made without forming a sharp crease, usually while the paper is damp (see Wet-folding)

Split-face edge module - an edge module which extends to the centre of symmetry of both the adjacent faces.

Squarism - a slightly derogative word sometimes used to describe the belief that folding squares is somehow 'purer' than folding other rectangles.

Stellation - in mathematics a stellation is a form produced by extending the sides of a convex polyhedron until they intersect. In origami this term is often misused to mean any star-like form produced by adding pyramids to the faces of a convex polyhedron.

Surface - a sheet of paper has two surfaces. Homogenous paper has surfaces which are identical or closely similar, differentiated paper has surfaces which are easily distinguished from each other.

Swivel fold - a complex fold in which making one fold automatically entails making another in the opposite direction.

Tessellation - in origami a tessellation is a repetitive geometrical pattern of flat folds which is created by pre-creasing and twist-folding a single sheet of paper.

Unit origami - a translation of yunnito origami - the Japanese term for modular paperfolding.

Valley fold - see entry for Mountain fold

Vertex module - a module which forms one corner (or vertex) of a polyhedral model. See also edge module and face module.

Visible surface - those parts of the surfaces of the paper which remain visible after the model has been completed. Like the paper from which they are derived, visible surfaces can be homogeneous or differentiated.

Wet-folding - a technique invented by the Japanese paperfolder Akira Yoshizawa in which the paper is dampened before it is folded. Damp paper folds like cloth and does not take a crease. Folds set into damp paper become permanent once the paper dries. It is not possible to unfold such designs without dampening them again and therefire not possible to show that the paper has not been differentially stretched, thus losing its integrity as a folding medium.