Intercurrent and Concurrent

• (a.) Running between or among; intervening.
• (n.) Something intervening.
• (a.) Said of diseases occurring in the course of another disease.
• (a.) Not belonging to any particular season.

adjective

• Occurring or operating at the same time.
  • usage: "a series of coincident events"
  • synonyms: coincident, coincidental, coinciding, co-occurrent, cooccurring, simultaneous

• (a.) Acting in conjunction; agreeing in the same act or opinion; contributing to the same event or effect; cooperating.
• (a.) Meeting in one point.
• (n.) One pursuing the same course or seeking the same objects; hence, a rival; an opponent.
• (n.) One of the supernumerary days of the year over fifty-two complete weeks; -- so called because they concur with the solar cycle, the course of which they follow.
• (a.) Conjoined; associate; concomitant; existing or happening at the same time.
• (a.) Joint and equal in authority; taking cognizance of similar questions; operating on the same objects; as, the concurrent jurisdiction of courts.
• (n.) One who or that which, concurs; a joint or contributory cause.