active support of an idea or cause etc.; especially the act of pleading or arguing for something
"The organization dedicated its resources to advocacy for clean water access in developing regions."
the profession of an advocate
"After years of legal advocacy, she finally secured a landmark victory in the high court."
In plain English: Advocacy is when you speak up to support and defend someone else's rights or interests.
"The local group showed great advocacy for improving public transportation in their city council meeting."
The word "advocacy" entered English via the Middle French form advocacie, which itself came from Medieval Latin. It originally referred to the office or function of an advocate before evolving into its modern sense of public support for a cause.