/ ˌɪnfluˈenʃl; NAmE / adjective
influential (in sth / in doing sth) having a lot of influence on sb/sth :
a highly influential book
She is one of the most influential figures in local politics.
The committee was influential in formulating government policy on employment.
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WORD ORIGIN
late 16th cent. (referring to astral influence): from medieval Latin influentia inflow, from Latin influere , from in- into + fluere to flow.