Origami Vocabulary Quiz

A valley fold and a mountain fold are the two most basic origami folds and they are opposites. In a valley fold, you fold the paper towards yourself, so the crease forms a dip like a valley; it is drawn as a dashed line. In a mountain fold, you fold the paper away from yourself, so the crease forms a raised ridge like a mountain; it is drawn as a dash-dot line. Almost every origami model is built from combinations of these two folds.

A pleat is made by combining a valley fold and a mountain fold right next to each other, which creates a folded step or zigzag in the paper. Pleats are used to add accordion-like texture, shorten the length of a flap, or create details such as feathers, scales, and fringes. Multiple pleats in a row form an accordion or fan pattern.

A reverse fold changes the direction of a point along an existing crease — an inside reverse fold tucks the paper inwards, while an outside reverse fold wraps it around the outside; both are common for forming heads, beaks, and feet. A squash fold, by contrast, opens up a folded flap and flattens it symmetrically over a centre crease to create a new shape such as a square or a petal base. Both are essential intermediate techniques.

A sink fold inverts a point of the paper, pushing it inwards and downwards so it 'sinks' into the model instead of sticking out. It is considered advanced because the paper must usually be pre-creased and partially unfolded before the point can be reversed cleanly, requiring careful control of multiple layers at once. Open sinks and closed sinks are two common variations.

A petal fold lifts a single flap of paper upward and narrows it by folding the side edges into the centre line, producing a slim, pointed, petal-like shape. It is one of the defining steps in making the bird base, which is the foundation for the crane and many other models, and it is also widely used in folding flowers, where the pointed shapes become petals.

A crimp is a pair of close, parallel folds — one valley and one mountain — that together bend or angle a section of paper without changing its overall length. Crimps are commonly used to create a neck, to bend a leg or tail, or to add a small change of direction to a narrow flap. Because the two folds work as a unit, a crimp can be adjusted to set a precise angle.

Origami tessellation is a technique in which a single sheet of paper is folded into a repeating geometric pattern that tiles the surface with no gaps or overlaps. The folds — often combinations of pleats and twist folds — interlock to form intricate designs that can include stars, hexagons, and lattices. Tessellations are admired for their mathematical precision and often look striking when held up to light.

Regular origami is usually folded from a single sheet of paper, while modular origami uses many separate sheets folded into identical units called modules. These modules are then locked together — without glue or tape — using flaps and pockets to build a larger structure, such as a geometric ball, star, or polyhedron. Modular origami combines folding skill with assembly and is popular for decorative, three-dimensional designs.

Wet folding is a technique in which the paper is lightly moistened with a damp cloth before and during folding. The dampness makes the fibres flexible, allowing the folder to create gentle curves and rounded, sculptural shapes instead of sharp creases. As the paper dries, it hardens and holds these soft forms. Wet folding is favoured for lifelike animals and elegant, organic models, and it works best with thicker, sized papers.

ESL learners exploring origami or craft instructions should prioritise: valley fold, mountain fold, pleat, reverse fold, squash fold, petal fold, sink fold, crimp, tessellation, modular, crane, and wet folding. These terms appear in instruction diagrams, craft books, video tutorials, and workshop classes, making them useful for following step-by-step directions and joining hobby communities in English.