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cir·cuit (sûrkĭt)
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n.
1.
a. A closed, usually circular line that goes around an object or area. See Synonyms at circumference.
b. The region enclosed by such a line.
2.
a. A path or route the complete traversal of which without local change of direction requires returning to the starting point.
b. The act of following such a path or route.
c. A journey made on such a path or route.
3. Electronics
a. A closed path followed or capable of being followed by an electric current.
b. A configuration of electrically or electromagnetically connected components or devices.
4.
a. A regular or accustomed course from place to place; a round:a salesperson on the Detroit–Minneapolis–Chicago circuit; a popular speaker on the lecture circuit.
b. The area covered by such a course, especially by the judge or judges of a court.
5.
a. An association of theaters in which plays, acts, or films move from theater to theater for presentation.
b. A group of nightclubs, show halls, or resorts at which enterners appear in turn.
c. A series of competitions held in different places.
intr. & tr.v.cir·cuit·ed, cir·cuit·ing, cir·cuits
To make a circuit or circuit of.

[Middle English, circumference, fromOld French, fromLatincircuitus, a going around, frompast participle ofcircumīre, to go around : circum-, circum- + īre, to go; see ei- in the Appendix of Indo-European roots.]
(click for a larger image)
circuit
top: Bulbs in a series circuit are dim because electricity has to pass through every bulb in the circuit before returning to the battery.
bottom: Bulbs in a parallel circuit shine brightly because each bulb has its own circuit that connects directly to the battery.

The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2016 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
 

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