Joti jot is a Punjabi phrase which literally means the "light joining another light" and is used to refer to the "joining of the light of the human person (soul) to the Supreme Light (God)". It is a term that is customarily used to refer to the "accession of a honoured person to their heavenly abode". In simple terms, this is a polite and honourable term used to refer to the "death" of a respected, honoured and blessed person. In its original language, it is a term which is polite, respectful and traditional. When referring to the death of the Sikh gurus, this term is commonly used.
The Sikh scriptures teach that the soul is indestructible and survives for eternity. When the person dies, it is only the body that is destroyed; the soul carries on its journey of reincarnation until it becomes pure and sinless so that it can blend with the pure Lord. So when the body of a person who is pure and one who has lived a life of righteousness dies, the soul of this perfect person is said to join the Almighty God. The act of joining with the Lord is referred to as "Joti jot samana" (Sah-ma-na means to "merge")
The Gurus tell us that the person's soul is immortal and that the soul never dies and is never born. However, the soul travels through many lives where the soul experiences birth and death while living within various bodies. This cycle of births and death only stops when the soul attains salvation or Mukti when it leaves this existence in moral bodies and joins the immortal supreme soul (god). The person is then said to have rejoined with God. This special condition is referred to as "Joti Jot" in Punjabi.