When two or more transformations are combined to form a new transformation, the result is called a composition of transformations, or a sequence of transformations. In a composition, one transformation produces an image upon which the other transformation is then performed.
(communitive and non-communitive)
The composition of reflections over two intersecting lines is equivalent to a rotation. ... A glide reflection is the composition of a reflection and a translation, where the line of reflection, m, is parallel to the directional vector line, v, of the translation.