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Ever wondered what a kite fold was? A uniaxial base? A closed sink? This glossary lists definitions for some common English-language origami terms (and a few uncommon ones as well).
Arrowhead molecule : a crease pattern within a quadrilateral that consists of a Waterbomb molecule combined with an angled dart; it allows an arbitrary four-circle quadrilateral to be collapsed while aligning the four tangent points.
Base : a regular geometric shape that has a structure similar to that of the desired subject.
Blintzing : folding the four corners of a square to the center
Box pleating : a style of folding characterized by all folds running at multiples of 45°, with the majority running at multiples of 0° and 90° on a regular grid.
Circle : the geometric shape within a circle-packed crease pattern that represents a leaf edge in the tree graph. That is, the circle identifies the minimum paper that must be allocated for a free flap.
Crease : a mark left in the paper after a fold has been unfolded.
Decreeping : rearranging several trapped layers of paper so that no layer is wrapped around another.
Distorted base : a modified base formed by shifting the vertices of the crease pattern so that the paper can fold flat; the number of creases and vertices remains the same, but the angles between them change.
Double-blintzing : folding the four corners of a square to the center twice in succession.
Efficiency : a measure of how much paper is used to obtain features of the subject versus extra paper that is merely hidden away.
Four-circle quadrilateral : a quadrilateral formed by connecting the centers of four pairwise tangent circles; such a quadrilateral can be folded so that all edges lie on a line and the tangent points between pairs of circles touch.
Generic form : a crease pattern within a molecule or group of molecules in which (a) all axial creases are shown as mountain creases; (b) all ridgeline creases are shown as valley creases; and (c) all hinge creases are shown as unfolded creases. The generic form is an approximation of the actual crease pattern of a folded base.
Gusset : one or more narrow triangles of paper, usually formed by stretching a pleat or crimp.
Gusset molecule : a crease pattern within a quadrilateral that resembles a partially stretched Waterbomb molecule with a gusset running across its top. The gusset molecule, like the arrowhead molecule, allows any four-circle quadrilateral to be collapsed while aligning the tangent points.
Hex pleating : a design technique similar to box pleating but that uses triangles, hexagons, and hexagonal rivers for packing and all creases run at multiples of 30°. Occupies a role halfway between circle packing and box pleating in terms of both efficiency and regularity.
Inflation : the process of adding circles to a crease pattern (corresponding to adding flaps to a base) and expanding the circle (lengthening the flap) until it touches 3 or more others. Inside reverse fold (page 25): a method of changing the direction of a flap, wherein the moving layers are inverted and tucked between the stationary layers.
Molecule : a crease pattern which when folded flat has its perimeter lie along a common line and for which specified points along the perimeter (the tangent points) become coincident in the folded form.
Offset base : a modified base formed by shifting the entire crease pattern on the square while preserving angles between creases, so that extra paper is created in some locations while others lose paper.
Origami : the art of folding paper into decorative shapes, usually from uncut squares.
Path conditions : the set of all inequalities relating the coordinates of the leaf vertices, the distances between their corresponding nodes, and a scale factor. The distance between any two vertices must be greater than or equal to the scaled distance between their corresponding nodes as measured along the tree.
Pythagorean stretch : a technique in box pleating in which two diagonally-oriented leaf vertices are allowed to move closer to each other than the square packing would normally permit. This results in the creation of axial creases and ridgeline creases at angles other than 0°, 45°, and 90° in the vicinity of the stretch but permits greater efficiency in the crease packing.
Reverse fold : a way of changing the direction of a flap by folding different layers of the flap in different directions. The two most common forms are the inside reverse fold and the outside reverse fold.
Stub : a new edge added to the tree graph attached to a new node introduced into the middle of an existing edge and associated creases added to the crease pattern. Adding a stub allows four path conditions to be simultaneously satisfied as equalities.
Tile : a portion of a crease pattern, usually consisting of one or more axial polygons and decorated by circles and rivers, that can be assembled into crease patterns by matching circle and river boundaries.
Tree theory : the body of knowledge that describes the quantitative construction of crease patterns for uniaxial bases based on a correspondence between features of a tree graph and features in the crease pattern.
Waterbomb condition : a quadrilateral satisfies the Waterbomb condition if and only if the sums of opposite sides are equal. A quadrilateral that satisfies this condition can be folded into an analog of the traditional Waterbomb Base.
If you would like to contribute a term and definition to this glossary, please send the term and its definition to the WebTeam, and we'll add it at the next opportunity.