Definition of amplitude in US English:



  • 1Physics
    The maximum extent of a vibration or oscillation, measured from the position of equilibrium.

    • ‘Lifetimes and the ratio of initial amplitudes remained constant at all energies.’
    • ‘To compare the relative amplitudes of the different spectra, it is necessary to normalize the signal.’
    • ‘It keeps its shape, even at large amplitudes, because the speed of waves in the medium depends on frequency in just the right way.’
    • ‘A frequency response of the transmission line is computed based on the measured amplitudes.’
    • ‘Vibrations and amplitudes are higher, giving heavier densities at a higher speed.’
    1. 1.1 The maximum difference of an alternating electrical current or potential from the average value.
      • ‘Practical researchers are only too aware, however, that the optical output can frequently vary significantly in amplitude and spatial quality from point to point within a crystal.’
      • ‘A problem with evoked potentials is that their amplitude is exceedingly small.’
      • ‘This local depolarization is known as an excitatory synaptic potential, and its amplitude is determined by the number of vesicles released from the presynaptic cell.’
      • ‘The correlation between changes in the kinetics of synaptic current and quantal amplitude remains strong for the corrected values as well.’
      • ‘Isochronal tail current amplitudes were normalized to the maximum amplitude obtained from that oocyte and plotted versus test potential.’
  • 2Astronomy
    The angular distance of a celestial object from the true east or west point of the horizon at rising or setting.

    • ‘Finally, we evaluate the reliability of the amplitudes and phases determined in the initial study of the star's amplitude and frequency variability.’
    • ‘The star's amplitude is approximately 0.1 magnitude.’
    • ‘In contrast, in a binary star system both components emit their own light, making possible much larger amplitudes in the variation of the total light received in our telescopes.’
  • 3Breadth, range, or magnitude.

    ‘the amplitude of the crime of manslaughter lies beneath murder’
    • ‘And also, given its magnitude, you know, the amplitude increases greatly with each point on the scale.’
    • ‘During these same thirty years or more, Sam has also become a writer of true amplitude: of outrage and forgiveness, of directness and intelligence, of tenderness and generosity.’
    • ‘Families, the overlapping and intersecting lines of emotions connecting parents and children, husbands and wives, the ‘dangerous mix-ups’ of domestic life - these are the subjects she returns to in these stories and she delineates them with an old-fashioned amplitude of emotion and language.’
    • ‘Past the half-mark, it morphs into a more ambitious and complex construction as the strings are given more scope and amplitude, but as they soon retract to the background, the original airy structure returns.’
    • ‘There is none of the heft and amplitude of real literature, none of the complexity.’
    • ‘What is missing is a certain largeness of mind, an amplitude of style, the mantle of a calling, a sense of historical dignity.’
    • ‘I was ‘stealing’ some movements and gestures but I had a different coordination, different amplitude of movement.’
    • ‘The lyrics have a breadth and amplitude of style that mark no common master of the poet's craft.’
    magnitude, size, volume, proportions, dimensions
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  • 4Mathematics
    The angle between the real axis of an Argand diagram and a vector representing a complex number.

    • ‘The amplitude of the observed dihedral angle distributions ascertains the flexibility of the secondary structure which never remains flat or adopts a reversed saddle shape.’
    • ‘The same experimental database is analyzed here for distributions of amplitudes and widths.’
    • ‘After covering the basics, he launches into a fairly academic discussion of signal and fourier analysis, and amplitude, angle and pulse modulation and demodulation.’
    • ‘A sine function has amplitude, phase, period and shift, and you can play tricks with these.’


Mid 16th century (in the senses ‘physical extent’ and ‘grandeur’): from Latin amplitudo, from amplus ‘large, abundant’.