taking gote in error
The difference between Sente or gote can be large. If you do the same thing in gote that could also be done in sente, that is a big difference - you lose a whole move. Players obviously will prefer sente sequences, other things being equal.
(We assume that the region to the right is Black's territory.)
takes gote. White has made a local gain. Black's threat is at a, OC, which transposes to the next diagram.
If Black plays first in the original position, captures the stones. But now if , Black will not respond at . This shows why is gote in the above diagram.
By the sacrifice of , Black takes sente.
Question: In this position White plays elsewhere, has Black taken sente? Or to put it another way, is this a very good example of the subject in question. I don't say that I am right or wrong, only that I am unconvinced. Black's best local follow up seems to be at a, which is not obviously a must answer move.
Miai analysis follows. 2nd diagram is the questionable part, as black may have better alternatives to . This analysis presumes and are sente.
There is no in the second diagram on this page.
Referring to the second diagram below this text. Added a pointer next to the diagram.
[This diagram has been edited. Previously, black mistakenly got the - exchange in sente, which is impossible.)