The word Allah (الله) is the Arabic term for Elohim.
In Islam, Allah is the essential personal name of God and comprises all His Beautiful Names (the 99 Names of God). When Allah is said, the One, the Supreme Being, the Creator, the Owner, the Sustainer, the All-Powerful, the All-Knowing, the All-Encompassing, whose Names and Attributes are manifested in creation, comes to mind. This term also refers to His absolute Oneness as well as His having no internal defect or external partner. In Arabic, the name is composed of four letters, ا ل ل ه (or Alif Lam Lam Ha) which when brought together make الله. Arab Christians believe that Allah consists of the Father, Son and Spirit, that together constitutes complete Allah.
Allah was the name of the moon god of the pre-Islamic polytheistic religion.