concurrent

adj

1. Happening at the same time; simultaneous.

   “concurrent echo”

   “Such are the changes which science recognizes in the wire itself, as concurrent with the visual changes taking place in the eye.”

   “In 1915, concurrent with the L.S.W.R. electrification, power was supplied from the Waterloo sub-station, and the old equipment held in reserve. Some generator sets were removed, and motor generators installed for standby lighting and other services.”

2. Belonging to the same period; contemporary.
3. Acting in conjunction; agreeing in the same act or opinion; contributing to the same event or effect.

   “I join with these laws the personal presence of the king's son, as a concurrent cause of this reformation.”

   “the concurrent testimony of antiquity”

4. Joint and equal in authority; taking cognizance of similar questions; operating on the same objects.

   “the concurrent jurisdiction of courts”

5. Meeting in one point.
6. Running alongside one another on parallel courses; moving together in space.
7. Designed to run independently, rather than sequentially, using various mechanisms, such as threads, event loops or time-slicing.

   “Informally, a concurrent program is one that does more than one thing at a time. […] However, this simultaneity is sometimes an illusion.”

   “Different concurrent designs enable different ways to parallelize.”

   “More precisely, a concurrent algorithm (or concurrent program) is the description of a set of sequential state machines that cooperate through a communication medium, e. g., a shared memory.”

   “Many languages are dogmatic about the solutions they offer for handling concurrent problems. For example, Erlang has elegant functionality for message-passing concurrency but has only obscure ways to share state between threads.”

noun

1. One who, or that which, concurs; a joint or contributory cause.

   “To all affairs of importance there are three necessary concurrents […] time, industry, and faculties.”

2. One pursuing the same course, or seeking the same objects; hence, a rival; an opponent.

   “Menander […] had no concurrent in his time that came neere vnto him”

3. 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.
4. One who accompanies a sheriff's officer as witness.