grass roots

(noun) the essential foundation or source. Synonyms: grass roots. Example: "The problem was attacked at the grass roots."

(noun) the common people at a local level (as distinguished from the centers of political activity). Synonyms: grass roots.

(adj) fundamental. Synonyms: grassroots. Example: "The grassroots factor in making the decision."

(adj) of or involving the common people as constituting a fundamental political and economic group. Synonyms: grassroots. Example: "A grassroots movement for nuclear disarmament."