abatis, axiom, axis, bottom, brains, center, center of action, center of gravity, centroid, centrum, chitterlings, cockscomb, core, dead center, distillate, distillation, elixir, epicenter, essence, essential, essentiality, fabric, flower, focus, fundamental, giblets, gist, gizzard, gravamen, haslet, heart, hub, hypostasis, inner essence, kernel, kidneys, liver, material, matter, meat, medium, medulla, metacenter, middle, nave, navel, nub, nucleus, nuts and bolts, omphalos, pith, pivot, postulate, principle, quid, quiddity, quintessence, quintessential, sap, soul, spirit, storm center, stuff, substance, sum and substance, sweetbread, the nitty-gritty, tongue, tripe, umbilicus, virtuality