Template:M summ Equity Derivatives 1.26

Relevant to Market Disruption Event. See also the related definition at "Exchange”.

In each case, the relevant Exchange or Related Exchange is simply the exchange specified as such in the Confirmation.

There is a corresponding fallback to substitute exchanges (what we our our nutshelly way call “Alternative Exchanges”) to which trading has temporarily located, although it is expresses slightly differently (more succinctly) here.

And the difference between Exchange and Related Exchange is what exactly?

The difference between the two is the inclusion in Related Exchange of the “All Exchanges” proviso. In practice this is what you tend to see — “Related Exchanges”, if used, is set to “All Exchanges”:

...provided, however, that where “All Exchanges” is specified as the Related Exchange in the related Confirmation, “Related Exchange” shall mean each exchange or quotation system where trading has a material effect (as determined by the Calculation Agent) on the overall market for futures or options contracts relating to such Index or such Share.