What is spiritual death, according to the Bible?

Spiritual death is separation from God. According to Genesis 2:17 and Romans 6:23, as a result of Adam's sin in the Garden, all human beings are born spiritually dead, captives of “the domain of darkness” (Col. 1:13). This means we are separated from our Creator and unable to function in our spiritual realm. At salvation, positional death occurs, separating us from sin and the sin nature, allowing us to choose between serving our old or new nature (Rom. 6:1–4, 10–11; Gal. 2:20). Temporal death is carnality, a separation from fellowship with God that happens every time we give in to temptation to sin (James 1:15; Rom. 8:2, 6, 13). Operational death occurs when our profession of faith is separated from the practice of that faith (James 2:26; Eph. 5:14; 1 John 1:5–6). Spiritual death is the root of all other deaths, and it's essential to understand this concept to grasp the depth of sin's impact on humanity. Through Christ's death, we have been freed from sin and its consequences, and can now live a new life in fellowship with God.