The boundary line of a figure, area, or object.(noun)
The length of such a boundary.(noun)
American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Use "circumference" in a sentence
"It follows directly from this discussion, that for our sphere-beings the circumference of a circle first increases with the radius until the circumference of the universe is reached, and that it thenceforward gradually decreases to zero for still further increasing values of the radius."
"This means the circumference is about 1000 meters, so v is 1000 meters per minute, which yields a simulated gravity about 1/6 of Earth's -- the same as the moon (though the people inside move as though the gravity is Earth-normal)."
"Paul Rodriguez was a Mexican porter who from the upper and lateral part of his head had a horn 14 cm in circumference and divided into three shafts, which he concealed under a cap."