An exposure (noun)

On this website, a photographic “exposure” refers to the uninterrupted period from when the sensor or film first begins recording light from the scene to when that recording is first interrupted or ended by any means.

“By any means” includes ending the exposure by closing the shutter, electronically stopping the recording of light, putting the lens cap or a black cloth on the front of the lens, or keeping by any other method the light from the scene from being recorded by the recording surface.

That particular exposure cannot continue once interrupted.

Any subsequent recording of light from the scene constitutes a separate exposure.

FURTHER READING

Guide to combining exposures in TTG photographs

Long exposures and the “sasibe” standard

See also Definition #1 of a “moment”