These adjectives mean existing or occurring at the same time. Contemporary is used more often of persons, contemporaneous of events and facts: The composer Salieri was contemporary with Mozart. A rise in interest rates is often contemporaneous with an increase in inflation.Simultaneous more narrowly specifies occurrence of events at the same time: The activists organized simultaneous demonstrations in many major cities.Synchronous refers to correspondence of events in time over a short period: The dancers executed a series of synchronous movements.Concurrent implies parallelism in character or length of time: The mass murderer was given three concurrent life sentences.Coincident applies to events occurring at the same time without implying a relationship: “The resistance to the Pope's authority . . . is pretty nearly coincident with the rise of the Ottomans” (John Henry Newman). Concomitant refers to coincidence in time of events so clearly related that one seems attendant on the other: He is an adherent of Freud's theories and had a concomitant belief in the efficacy of psychoanalysis.