define nidus
nidus niÂ·dus (nÄ«'dÉs) n. pl. niÂ·dusÂ·es or niÂ·di (-dÄ«) A central point or focus of bacterial growth in a living organism. A nest, especially one for the eggs of insects, spiders, pathogenic organisms, or small animals. A cavity where spores develop. A point or place at which something originates, accumulates, or develops, as the center around which calculi form.