Tl;dr heres the pluralpedia link https://pluralpedia.org/w/Modular

A modular system is a system whose fragments will come together to create flares (temporary alters) specific to any given situation.

So for example fragment 'social around family', 'cautious', and 'agab holder' might merge together temporarily for a an event where homophobic family is around to create a flare.

Flares may have a name, pronouns, and identity before the fragments seperate again, the flare disapearing.

This can cause a lot of amnesia if memories disapear with the flare, but could also cause minimal amnisia if the fragments get to keep the memories they were a part of.

Modular systems can often look like polyfragmented and/or median systems as well as cyclogenic, and many people will identify with those terms before they find modular.

we ourselves identified with all of those at previous points in our discovery.