First, to clarify a long-held mistranslation:
There is no such Commandment saying “Thou shalt not kill”. CORRECTLY translated from Hebrew into English, it is “Thou shalt not MURDER”! Some people might think they are one and the same, but that is not true.
THE major difference is this: MURDER is done “with malice aforethought”. In other words, it is premeditated. It is planned out ahead of time.
KILLING, on the other hand, can be done in self-defense, as part of a war, or by accident. For example, suppose you are driving down your road in the winter, and hit a patch of black ice. It is not unreasonable to think you could lose control of your car, and that the resulting skid might wind up hitting a pedestrian…who dies as a direct result of the injuries. Now, was this all “premeditated”? Was it a deliberate act? In both cases, the answer is a resounding “NO!” It was an accident, and no jury is likely to convict anyone of murder for what was really just an accident.
Now, if you had said "Tomorrow morning, I am going to end the life of “X”…and you do it…THAT is murder!
God, being all-knowing and Omniscient, would know Himself if it was a purposeful act of ending the life of an innocent person. That’s why many of us agree that abortion is murder: It is a deliberate act that ends the life of an innocent human being. Nobody has that “right”!