Arabs are a major panethnic group whose native language is Arabic, comprising the majority of the Arab world. They primarily inhabit Western Asia, North Africa, and parts of the Horn of Africa. Before the spread of Islam, Arab referred to any of the largely nomadic Semitic tribes inhabiting the Arabian Peninsula. In modern usage Arabic-speaking populations are a highly heterogeneous collection of peoples, with diverse ancestral origins and identities. The ties that bind the Arab people are common linguistic, cultural, and political traditions. As such, Arab identity is based on one or more of genealogical, linguistic or cultural grounds, although with competing identities often taking a more prominent role, based on considerations including regional, national, clan, kin, sect, and tribe affiliations and relationships. If the Arab panethnicity is regarded as a single population, then it constitutes one of the world's largest groups after Han Chinese and Indo-Aryan Indians.
The Arabian Peninsula itself was not entirely originally Arabic. Arabization occurred in some parts of the Arabian Peninsula. For example, the language shift to Arabic displaced the indigenous South Semitic Old South Arabian languages of modern-day Yemen and southern Oman. These were the languages spoken in the civilizations of Sheba, Ubar, Magan, Dilmun, and Meluhha— whose origin is debated; Lionel Bender (1997) suggesting an origin in Ethiopia, while others suggest the southern portion of the Arabian peninsula. A recent (2009) study based on a Bayesian model to estimate language change concluded that the latter viewpoint is more probable.