Define “memory”. If you think “react differently to the same stimulus as before not because of sensory or motor fatigue” requires a memory, single-cell organism

Define “memory”. If you think “react differently to the same stimulus as before not because of sensory or motor fatigue” requires a memory, single-cell organisms may qualify (Google “habituation in single cell organisms”, and find, for example https://en.wikipedia.org/wiki/Habituation https://en.wikipedia.org/wiki/Habituation, https://www.sciencealert.com/this-single-celled-animal-can-make-complex-decisions-even-without-a-nervous-system https://www.sciencealert.com/this-single-celled-animal-can-m...)