the act of concurring.

accordance in opinion; agreement

With the concurrence of several specialists, our doctor recommended surgery.

cooperation, as of agents or causes; combined action or effort.

simultaneous occurrence; coincidence

the concurrence of several unusual events.

Geometry . a point that is in three or more lines simultaneously.

Law . a power equally held or a claim shared equally.

Archaic . competition; rivalry.

noun

accord , concord , concordance , consonance , harmony , rapport , tune , unity , simultaneity , synchroneity , synchronism , unanimity

adjective

synchronistic , synchronous

verb

agree , concur