The answer
The Greek word "Epi-osios" has more than one meaning, even the early fathers of the church differed in translating this word.
+ St. Jerome's Vulgate translated it to "substantial bread" or "over super substantial bread" which means in Latin "panem nostrum super substantial" and so did Origen.
+ While St. Augustin and St. Gregory, bishop of Nyssa, translated it to "our daily bread" which in Latin "panem nostrum quotidianum".
+ St. John Chrysostom also used the same phrase "our daily bread" in his commentary on the Gospel of St. Matthew (Article 19 - Section 8).
+ The Coptic translation, which is considered one of the most known and trusted translations used the phrase "our bread for the morrow".
+ The English translation, (king James Version, and the New Revised Standard Version) says "our daily bread" and in the margin it says "our bread for the morrow".
I do not intend to put you in a linguistic rebuttal, as I do not want to bring up what the other fathers said in explaining the Lord's prayer for that will not benefit you in any way.
Furthermore, I do not want to make your prayer time a time for linguistic debates, so during prayers someone may attempt to raise his voice to dominate the voice of others, or to show that he knows what is better, or to make himself a leader or an example for the others to follow. This way the prayer itself will lose the spiritual goal which is the conversation with God to be a scientific rebuttal...! we do not need that in our spiritual life.
Basically, it is enough to understand one fact during the time of prayer which is that the bread that we are asking for, is the spiritual bread necessary to our eternal life.
We say that having in mind the following points:
1. The Lord's prayer is composed of 7 requests. The first three requests are pertinent to God.
a. Hallowed be Your Name. b. Your kingdom come. c. Your will be done.
The other four requests concern us, they start with "our bread"... and it is illogical for us to start our requests by asking for material food before we ask for the forgiveness of our sins and before asking to he rescued from temptations and all evil.
2. This also contradicts what the Lord said: .."therefore I say to you, do not worry about your life, what you will eat or what you will drink..."therefore, do not worry saying what shall we eat? or what shall we drink?... for after all these things the Gentiles ask... but seek first the kingdom of God and His righteousness, and all these things shall be added to you. " (Matt. 6:25,31-33). " Do not labor for the food which perishes, but for the food which endures to everlasting life, which the Son of Man will give you, because God the Father has set His seal on Him " (John 6:27).
3. Nevertheless, if we need the bread we should ask for it but then we should ask for our daily bread, not worrying about the morrow. That what St. Gregory of Nyssa and St. John Chrysostom have said, we here ask for the bread not the pleasures of foods.
4. If we say "our bread for the morrow" what do we mean?
The bread necessary for our souls, our eternity and for our future life, the morrow... and here we should put in our hearts to ask for all the foods of the spirit as prayer, contemplation, love of God, contiguity to God and as partaking of the Holy Communion.
Notice here that the Coptic translation was spiritual in understanding this request.
5. If some say "our daily or sufficient bread," that means the material bread if it is lacking... or, alternatively, the spiritual bread that is needed for their satisfaction, lest they should fall into sin or luke warmness, nor more than they need lest they fall into vain glory or conceit.
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Thrice-Blessed Pope Shenouda III of Blessed Memory