Interstitial

Interstitial is a generic term for referring to the space between other structures.

In crystallography, interstitial space refers to the open spaces within the crystal lattice.

In anatomy, interstitial cells are cells found in the spaces between organs and other tissues. Similarly, interstitial fluid is the fluid between organs and tissues, outside of the lymphatic or cardio vascular systems.

The word derives from the Latin interstitialis, literally 'placed between', from inter: between, and sistere-stiti-statum: to place.