Scansion is an analytical process that illustrates the extent to which a poem's normative rhythmical patterning – its metre – is realized in its individual lines. All language is rhythmical; what makes metrical different from non-metrical language is not therefore that metrical language has rhythm, but that its rhythm is marked by a phonological feature (stress, or pitch or length) that recurs in predictable patterns: it is this patterning that defines a poem's metre, and which is the object of interest in scansion. Analysis of rhythm on its own terms, as something sui generis, without a sense of how that rhythm might be part of (or depart from) a given poem's metre is not scansion, but “phrasing”. …
Hurley, Michael D.. "Scansion". The Literary Encyclopedia. First published 08 September 2008; last revised 30 November -1.
[http://www.litencyc.com/php/stopics.php?rec=true&UID=986, accessed 25 April 2015.]