Boundary condition is a phrase that is used in various fields such as mathematics, physics, engineering and computer science. It represents a set of conditions or constraints that define the behavior of a system at its edge or boundary. There are numerous synonyms for the phrase "boundary condition" such as edge condition, initial condition, boundary constraint, limiting condition, boundary value, boundary specification, boundary limit, boundary state, boundary parameter, and boundary requirement. These synonyms serve the same purpose as a boundary condition but are used interchangeably to provide a clear understanding of the system's boundary. Hence, these synonyms are crucial in determining and analyzing the behavior of a system at its boundary.