I am referring to Donald Pavia's Introduction to Spectroscopy, and I found this table that tells about the intensities of the peaks of vibrations of certain bonds.

enter image description here

I can't understand what s, m, w, w-s, etc. are supposed to mean. My guess is that s could mean small, m could mean medium and w could mean weak. But that's crazy, since small and weak mean the same thing? So what do they mean actually?

  • $\begingroup$ I'm quite sure this is described in the book itself. $\endgroup$
    – Mithoron
    Jun 27, 2017 at 15:35
  • $\begingroup$ @Mithoron Unfortunately it isn't. $\endgroup$ Jun 27, 2017 at 15:37
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    $\begingroup$ This is the tag for IR spectroscopy, ft is standard procedure. $\endgroup$
    – Mithoron
    Jun 27, 2017 at 15:44
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    $\begingroup$ @hBy2Py is correct. I have found a similar table on another page which is a bit more explicit in what its abbreviations mean and every thing lines up with the the notation of strong/ medium/ weak. www2.chemistry.msu.edu/faculty/reusch/virttxtjml/Spectrpy/… $\endgroup$
    – Tyberius
    Jun 27, 2017 at 16:54
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    $\begingroup$ It is described in the book, p 28 (5th ed) "Often, when reading the literature of organic chemistry, you will find absorptions referred to as strong (s), medium (m), weak (w), broad, or sharp." $\endgroup$ Jun 27, 2017 at 17:04

1 Answer 1


Given the general agreement surrounding my comment on the question and the similar abbreviations and descriptions in the chart on the page linked by Tyberius in his comment, the meanings appear to be:

  • strong
  • moderate (or medium)
  • weak

Notations such as m-w and w-s presumably indicate a peak intensity that is variable in the indicated range, depending on the properties of the particular molecule of interest.


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