"Form in a line" is a phrase commonly used to describe the act of lining up or organizing people or objects in a straight arrangement. Synonyms for this phrase include "queue up," "line up," "get in formation," "stand in line," "file in," "align," "assemble," and "marshal." Each of these words describes a slightly different nuance of the action of forming in a line, but they all refer to the same general idea of creating an orderly arrangement of people or objects. Whether you're waiting in line to board a plane or organizing a group of troops for battle, "forming in a line" is an essential component of many different activities.