A trading range is a stretch of chart in which price repeatedly turns near the same upper boundary and the same lower boundary, with no net direction over the stretch as a whole. The two boundaries are drawn by the reader from prior turning points, so a range is a description imposed on the chart rather than something the chart publishes: widen the boundaries and more of the chart becomes a range, tighten them and less of it does.
Ranges are usually discussed together with the boundaries themselves, because the vocabulary for what happens at each edge — a turn back inside, a move outside that holds, a move outside that does not — is the same vocabulary used for support and resistance generally. A range also ends the moment it stops describing the chart, which can only be established afterwards: there is no point during a range at which the chart announces that the next turn will not come.
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