Dr. Zakir Naik: Lectures on various topics

Re: If Islam means Peace, then why does it preach JIhad?

the word islam has a two-fold meaning

*Definition
The word ISLAM has a two-fold meaning: peace, and submission to God. This submission requires a fully conscious and willing effort to submit to the one Almighty God. *

Is·lam (ĭs-läm’, ĭz-, ĭs’läm’, ĭz’-) pronunciation
n.

  1. A monotheistic religion characterized by the acceptance of the doctrine of submission to God and to Muhammad as the chief and last prophet of God.
    1. The people or nations that practice Islam; the Muslim world.
    2. The civilization developed by the Muslim world.

Arabic ’islām, submission, from ’aslama, to surrender, resign oneself, from Syriac ’ašlem, to make peace, surrender, derived stem of šlem, to be complete.

http://www.answers.com/topic/islam
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In Arabic, Islām means “submission” (understood as submission to God) and is described as a Dīn or Deen, meaning “way of life” and/or “religion.” Etymologically, it is derived from the same root as, for example, Salām meaning “peace” (also a common salutation). The word Muslim is also related to the word Islām and means one who “surrenders” or “submits” to God.