The state of being erect, or of having an erect posture(noun)
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Use "erectness" in a sentence
"This expansion frees the respiratory muscles and all the vital organs, gives man command of the elemental action of his body as a whole; that is, his erectness expresses higher emotions and experiences."
"The qualities that seem to have attracted Karin Boye in these poems are the ones associated with emotional and spiritual directness, or 'erectness' or 'straightness' - rakhet."
"And the boy, lean and lithe, sunbeaten and browned, skin-clad and in hair - fringed and hair-tufted MUCLUCS that showed the wear of the sea and rough work, coolly withstood her advances, his body straight and stiff with the peculiar erectness common to children of savage people."