In classical mechanics, a constraint on a system is a parameter that the system must obey. For example, a box sliding down a slope must remain on the slope. There are two different types of constraints: holonomic and non-holonomic.[1]
^Leach, Dr Andrew (2001-01-30). Molecular Modelling: Principles and Applications (2nd ed.). Harlow: Prentice Hall. pp. 369–370. ISBN9780582382107.