A Sunni is a Muslim who belongs to the larger of the two main branches of Islam. About four out of five Muslims in the world are Sunni. The word is also used as an adjective — a Sunni family, a Sunni mosque, Sunni Islam. The split with the other main branch, the Shia, goes back to a disagreement about who should lead the Muslim community after the Prophet Muhammad died. Sunnis held that the leader should be chosen by the community; Shias held that leadership belonged to the Prophet's family line. Two things are worth knowing, though. First, the two branches share far more than they differ on — the same God, the same holy book, the same five daily prayers, the same pilgrimage. Second, in the news you will often hear 'Sunni' and 'Shia' used as if they were teams in a war. In real life most people are simply born into one or the other, live next to each other, and marry each other; when there is fighting, the reasons are usually about power and land as much as about religion. So when a news report explains a conflict by saying 'Sunni versus Shia', treat that as a very short summary of something much more tangled. It is a normal, neutral word — a person can say 'I'm Sunni' the way someone here might say 'I'm Buddhist'. Always written with a capital S.