Precision alignment of imprints generated by two or more printing blocks or plates on the same sheet of paper, as when printing an image in several colors. Areas that will not print are cut away, leaving elevated areas to accept the ink. The result is a precise registration of the color images. Precision alignment of components during manufacturing processes to ensure proper function and fit between parts. For example, computer chips are aligned during packaging to ensure that all contain the same number of devices. Components may also be aligned using fixtures during testing or final assembly. The term "alignment" has other meanings in mathematics and physics. Alignment of objects in three-dimensional space is often required for them to function properly. In geometry, two lines or planes are said to be collinear or parallel if they intersect at a single point, called their intersection. If two lines are perpendicular to each other then they form a right angle. They are then said to be aligned. In physics, particles within an atom or molecule must be aligned in order for them to function properly. If they are not aligned properly, they would have different energy levels which could cause undesirable effects such as chemical reactions occurring at random times or temperatures outside of normal limits. In astronomy, the phrase "aligned galaxy" refers to two galaxies with similar properties that appear to be lying along the same line in space.