Definition of "impedance" []

• A measure of the total opposition to current flow in an alternating current circuit, made up of two components, ohmic resistance and reactance, and usually represented in complex notation as Z = R + iX, where R is the ohmic resistance and X is the reactance. (noun)
• An analogous measure of resistance to an alternating effect, as the resistance to vibration of the medium in sound transmission. (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.

• "‡ The term impedance is most often encountered in dealing with antennas and speakers in television, stereo, and radio systems."
• "One of the problems the middle ear has to overcome is the mismatch in impedance between air and the cochlea, but impedance matching by the middle ear results in only a 30 dB increase in sound energy transmitted to the inner ear."
• "Guts: One of the problems the middle ear has to overcome is the mismatch in impedance between air and the cochlea, but impedance matching by the middle ear results in only a 30 dB increase in sound energy transmitted to the inner ear."