Analysis of information sources in references of the Wikipedia article "Nyquist frequency" in English language version.
The Nyquist frequency is that frequency whose period is two sampling intervals.
The Nyquist rate is twice the bandwidth of the signal ... The Nyquist frequency or folding frequency is half the sampling rate and corresponds to the highest frequency which a sampled data system can reproduce without error.
the existence of power in the continuous signal spectrum at frequencies higher than the Nyquist frequency is the cause of aliasing error
{{cite book}}: CS1 maint: multiple names: authors list (link)Frequencies "fold" around half the sampling frequency - which is why the [Nyquist] frequency is often referred to as the folding frequency.