Death simply means SEPARATION.
To make it more clear know human beings have a body, soul and spirit. Body is obviously is my physical body. Soul is my mind, will and emotions. When we say my body, who is this “I”? The Creator gives us the right order in His word as the spirit, soul and body when He talks about man. The “I” is the spirit of the man who has a mind and he lives in a body.
The moment one receives Jesus Christ he receives the Holy Spirit and his spirit becomes one with the Spirit of God and he never dies ie he will never be separated from God and thus he has overcome death just as Jesus did on the cross when he rose from the dead defeating the last enemy that is death.
Thanks be to God Who loved us that He sent His Son Jesus to overcome death and gave us eternal life to all who would receive Him as it is in Him we have life.