When physicists say something is instantaneous, what do they actually mean?

Question: When physicists say something is instantaneous, what do they actually mean?
- Keywords:
  instantaneous,
  meaning,
  term
Asked by PatrycjaG on 25 Apr 2023.
- Benjamin Rienacker answered on 25 Apr 2023:
  
  Mostly, it is a word used to express that something takes only a very little time with respect to the other processes to which “this something” is compared to. An atomic excitation with a laser pulse length of few nanoseconds is typically assumed to be instantaneous, if occurring de-excitations take more to a lot more time, or the time simply does not matter. It is similar to what people mean when they say something is hot or cold. It depends on your definition of relative temperature, which can feel hot or cold to your skin.