Islam is a verbal noun originating from the triliteral root s-l-m which forms a large class of words mostly relating to concepts of wholeness, safeness and peace. In a religious context it means "voluntary submission to God." Muslim, the word for an adherent of Islam, is the active participle of the same verb of which Islām is the infinitive.... The word sometimes has distinct connotations in its various occurrences in the Qur'an. In some verses, there is stress on the quality of Islam as an internal conviction: "Whomsoever God desires to guide, He opens his heart to Islam."
Other verses connect Islām and dīn (usually translated as "religion"): "Today, I have perfected your religion (dīn) for you; I have completed My blessing upon you; I have approved Islam for your religion." Still others describe Islam as an action of returning to God—more than just a verbal affirmation of faith. In the Hadith of Gabriel, islām is presented as one part of a triad that includes imān (faith), and ihsān (excellence), where islām is defined theologically as Tawhid, historically by asserting that Muhammad is messenger of God, and doctrinally by mandating five basic and fundamental pillars of practice."
Islam - Wikipedia, the free encyclopedia