Here's a little discussion on the subject:
There are some significant differences in the Hebrew words that have been translated as "die" and "surely die" in the recording of the communications of the Lord, Adam, Eve, and the serpent. The quote from the Scriptures that follow are Word by Word translations from the "Interlinear Bible" by J. P. Green and following each passage there is a magnified selection from the "Interlinear Bible" which is included to show in detail the recorded Hebrew words that are translated as die in each Passage.
Notice that the Hebrew word ( Strong's # 4191 ) is repeated which is a technique often used in the Hebrew for emphasis and the last of the passage is often translated more literally as "dying thou shall die". A less literal translation is "for as soon as you eat of it, you shall be doomed to die". For we know from reading the rest of the story the penalty was not sudden physical death, but as soon as the disobedience occurred Adam and Eve's relationship with the Lord was drastically changed and they were reduced to hiding in the bushes, the penalties were soon announced, and they were banished from the garden to continue the rest of their life in toil and sorrows.
Notice that Eve did not repeat the form of the Words of the Lord! Instead she varied the Hebrew word translated as die and did not use the repeated word form used for emphasis. She also added the phrase about not touching it. The word form she used is unusual and similar forms appear only in Numbers 16:29 and Isaiah 22:14 and in both of these occurrences it appears to mean a physical death under conditions of judgment. It would appear that in her statement she was possibly showing her uncertainty or lack of full understanding as to exactly when and what would be the result of disobedience and the seriousness of the penalty. Eve would seem to have no way of knowing about death unless she had witnessed the physical death of a plant or an animal.
http://www.accuracyingenesis.com/die.html
