Episteme
"Episteme" is a philosophical term derived from the Ancient Greek word ἐπιστήμη "epistēmē", which can refer to knowledge, science or understanding, and which comes from the verb , meaning "to know, to understand, or to be acquainted with".
Epistemic community
An epistemic community is a network of knowledge-based experts who help decision-makers to define the problems they face, identify various policy solutions and assess the policy outcomes. The definitive conceptual framework of an epistemic community is widely accepted as that of Peter M. Haas. He describes them as 
"...a network of professionals with recognised expertise and competence in a particular domain and an authoritative claim to policy relevant knowledge within that domain or issue-area."