The first line of this prayer, "Hail Mary, full of grace", is actually rather theologically dense, and also a main point of contention among Protestants and Catholics. The first point of contention is actually that first word, "hail", which many view as being a sign of worship... Not so. 

     The word “hail”, for many, brings to mind an image of thousands of people on their knees, raising and lowering their hands while chanting: "All hail Mary! All hail Mary!...." But this, no matter how popular an image on television, is completely false. Let's ask ourselves, what does the word "hail" ACTUALLY mean? 

" Webster’s New World Dictionary (2005)” defines the word as:

(interjection) "used to express acclimation"

(Verb) "1: Salute, Greet 2: Summon"

(Noun) "expression of greeting, approval, or praise"

     None of these, we should note, means "to worship", and in fact, in Latin, the word for hail (from which the prayer comes) is "Ave" and in fact, was the same word used by the Roman in their famous "Hail, Caesar", which was the greeting or salute that Roman soldiers would offer to each other, and to those above them. The  modern equivalency of which being a military salute, and in fact, we even see "salute" as one of the above definitions! 

     But don't take my word for it, take that angel Gabriel's word for it, for when he greeted Mary at the annunciation (when he announced she would conceive Christ), he spoke:

"Hail, full of grace, the Lord is with thee." (Luke 1:28) (confraternity version)

So it is that the words of the prayer are the very ones used by the angel Gabriel! These words, coming straight from scripture, could not be more scriptural! What the angel is saying here, and what we say when we repeat him, is essentially: "Hello, Mary, blessed by the Lord who is watching over you".

     The next part of this line is even more theologically dense, for the angel says that Mary is "full of grace", but this is only in the English translation… In Greek, the original language of the Gospels, the angel says, "Kecharitomene". This word actually denotes a perpetual state, meaning, "always has been, always will be, full of grace". To see the implications of this, we must evaluate what it means to be "full of grace". 

To be full of something means to have no room left over. Imagine a glass of oil. If the glass is full of oil, then there is no room for water, and if water were added, it would no longer be full of oil, for oil would come out. The water which we add is the sin, which separates us from God's grace, and to be full of grace means to have no sin. Thus, if Mary truly was perpetually full of grace, then this is an illusion toward Mary's "immaculate conception", which is a Catholic doctrine that states that Mary was conceived without original sin. 

     So as we can see, “Hail Mary” is a simple, yet formal, greeting, which comes from the angelic greeting in the Gospel of Luke. This greeting doesn't denote worship, otherwise the angel of God would be guilty of blasphemy! We can see also from this that “full of grace” is a very important and meaningful phrase, especially since it alludes to Mary’s Immaculate Conception. Another thing which we should also note is that the angel in the original text says “hail, full of grace” and omits the word “Mary”. Almost as if he is addressing her by the title Kecharitomene, showing the significance of the title, just as when we call Mary “the Virgin” it shows the significance of her virginity!