heart / core / center
Masculine noun. Plural: قُلُوبٌ (qulūb). In the Quran, the heart is the seat of understanding, faith, and spiritual perception - not just emotion.
The heart (qalb) in Quranic anthropology is the center of intellect, faith, and intention. A sound heart (qalb salīm) is what matters on Judgment Day (26:89).