Coming into force (also called enforcement or enactment) is a term that refers to the process by which legislation, or part of legislation, and treaties comes to have legal force and effect. The term is closely related to the date of this transition.
To come into force the treaty or act need to receives the requisite majority of votes or ratifications.
After their adoption, Treaties as well as their amendments have to follow the official legal procedures of the United Nations, as applied by the Office of Legal Affairs, including signature, ratification and entry into force.
It is important to note that the process whereby a bill becomes an act is an entirely different process from that of bringing the act into force. A bill which does not amount to an act--even though it is passed by law makers--cannot be of any force and effect.
A country's law could determine that on being passed by lawmakers, a bill becomes an act without further ado. However, more usually, the process whereby a bill becomes an act is well prescribed in general constitutional or administrative legislation. This process varies from country to country, and from political system to political system.