the act of accepting something
The far-right Sverigedemokraterna (the Sweden Democrats) is opposed to the European Union and against Sweden's adoption of the euro.
the act of putting a law, regulation, rule, plan etc into operation
The United States welcomes the Central African Republic's adoption of reforms, particularly those favoring increased press freedom
the act of taking legal responsibility for another person's natural child on the same grounds as if it was your own child
A group of parents in Sierra Leone have accused a charity of sending their children abroad for adoption without consent (=agreement).