Below content taken from http://www.islamtomorrow.com    First of all the words "Islam" and "Muslim" are Arabic, not English. They do not easily translate into one word. The word " MUSLIM  " is derived from the Arabic word   ISLAM  . So, let us begin by asking the question what does "Islam" mean anyway? Good question.  ISLAM  comes from the root "slm" or "salama" The word   ISLAM  in reference to the faith is understood in Arabic as the: 1) Surrender   2) Submission   3) Obedience   4) Sincerity   5) Peace All of which come about only by giving up the Free Will of the nafs (self or ego) in favor of the Will of the Creator and Sustainer of All That Exists (ALLAH). Now we should ask the logical question,  "What does the word MUSLIM  mean?" Again, we must keep in mind that it is an Arabic word and is of course subject to the rules of the Arabic language. Actually, it is derived from the word ISLAM. Whereas, you might think of ISLAM as the verb or action and MUSLIM  as the noun, or the one performing the action. In English whenever we have a noun performing a verb, we add the two suffix letters; ER. But in the Arabic language many times you will find that the prefix letters of MU are used for the same purpose. A few examples may help to better understand:  English Verb English Performer Arabic Verb Arabic Performer Travel Travel ER Safar MUsafar Call Call ER Adhan MUadhan Pray Pray ER Salah MU salah Submit Submit ER Islam MU slim "Muslim" is one who follows or practices the action of "Islam." In English we might say that any one who "Islams" is an "Islam-ER." Right? So as we see in the chart above, in Arabic the "mu" preceding a verb indicates the same thing. Therefore, we would understand that the one who is actively doing the verb of "Islam" [submission to God] is a "Mu"-Islam or "Muslim." Next,  we must ask when is it that person actually becomes a " MUSLIM  "? Only when a person gives up his or her free will in order to obey Allah completely on Allah's terms does he/she become a " MUSLIM  ."  Following along the orders of Jesus in the Bible when he tells his disciples to "Pray thus.... Thy Will be done on earth, as it is in Heaven." Also, Allah has told us in His Book that all of the creation is in submission to Him ( MUSLIM  ). {Inna deenah innda lahi, Islam.} (3:19) “Certainly, the only way [deen] acceptable to Allah is the submission to Him in Islam.” And again in Chapter Mayadah (5:3), when Allah Subhannah wa Ta’ala says: {Al yawmal akmal tu lakum deenakum wa atmumtu alaykum ni'mati wa raditu lakum al Islam adeena} “On this day have I perfected your way of life [religion] for you, completed My Favor upon you and have chosen for you ISLAM as your way of life. (sometimes translated as [religion].”