90gradig

90gradig is a term used in several Scandinavian languages to describe something that has a 90-degree angle or is aligned to form a right angle. The word combines the number 90 with the word for degree (grad) and the adjectival suffix -ig, or a hyphenated form in some orthographies. The expression is commonly applied to angles, lines, joints, and shapes in geometry, construction, design, and surveying.

In geometry, a 90-degree angle is called a right angle. When two lines intersect to form such an angle, they are perpendicular to each other. A right triangle contains one 90-degree angle, while a quadrilateral with all angles equal to 90 degrees is a rectangle, and a square is a special case of a rectangle with equal sides. The concept of right angles underpins many practical and theoretical ideas, including orthogonality in linear algebra, where vectors are considered orthogonal if the angle between them is 90 degrees and their dot product is zero.

In everyday use, 90gradig describes physical features that require precise perpendicularity, such as building corners, furniture joints, and architectural layouts. It also appears in phrases about rotation and orientation, where a 90-degree turn or rotation changes the facing direction by a quarter turn.

Etymologically, 90gradig reflects the combination of the numeral 90 with grad (degree) and adjectival suffixes in Germanic languages. The exact spelling may vary by language, with hyphenation common in some styles.