Word for larger system that is more than the sum of its constituents

I’m driving myself crazy because I’ve forgotten a word that I used to know. The word describes the phenomenon of a larger organised system that does more or has another function than the collective sum of its constituent parts.

Or the other way round when lots of bodies that have individual functions take on a new macroscopic role as a collective.

Does anyone know what the word I’m looking for is. I’ll recognise it when I see it and I appreciate there may be more than one word for this. It might be a scientific and/or psychology specific word.

Solution 1:

Emergence

an entity is observed to have properties its parts do not have on their own. These properties or behaviors emerge only when the parts interact in a wider whole.