The Encyclopaedia Britannica entry defines a think tank as an "institute, corporation, or group organized for interdisciplinary research with the objective of providing advice on a diverse range of policy issues and products" and categorizes them into four broad types: ideological (devoted to a particular political perspective), specialist (focused on a topic, such as children's health or environmental protection), regional, and "think and do" tanks (focused on not only policy but also conducting practical projects). (Ladi 2015)
Think tanks will often claim to be nonpartisan, but pay close attention: many of the "nonpartisan" groups' ideas may conveniently align with a particular political perspective (i.e. conservative, liberal/progressive, libertarian, etc.).
Ladi, Stella. (2015). Think tank. Encyclopaedia Britannica. Retrieved from https://www.britannica.com/topic/think-tank
