Measurement is Nucleus applied to a State — how observation consolidates what is.
Nucleus is closure in general — how things settle into the smallest closed structure containing them. Measurement is what Nucleus does to a particular State within a particular Profile. If State is “how things are right now,” Measurement is “how things are consolidated by observation.”
Where Evolution moves a State forward through Flow, Measurement closes a State down through Nucleus. Together they are the two operations Geometry produces when it acts on the contents of Profiles.
Measurement and Evolution interact through Residuation — the same residuation structure that has been present since Implication, governing the compatibility of complementary operations throughout the derivation.