Potomac

The name of the river on which Washington D.C. (the capital of the United States) stands is pronounced with the stress on the second syllable. The vowel sound in that is like the name of the letter 'o': 'pot-OH-mac', IPA: /pə (or ɒ) ˈtəʊ mæk/ - or /-ək/ or /-ɪk/.

Etymological note: Potomac is a transliteration of Patawomeck, an Algonquian (native American) name meaning 'trading place', incorrectly understood as naming the river on which it stood. It was recorded in the map published by John Smith (1580-1631) in 1606. Many other transliterations have been used since European settlement, such as Patomake, Pathamook and Patomic.

• The Army of the Potomac was a military force for the Union in the American Civil War (1861-65), which fought south of Washington DC. After losing the first battles of the war (including the First Battle of Bull Run, or Manassas, the Seven Days Battle, and the Second Battle of Bull Run, or Manassas), the Army of the Potomac repelled Lee's march on Washington at Antietam, or Sharpsburg in 1862. Chancellorsville (and two lesser engagements at Sharpsburg) in 1863 have been called Confederate general Robert E. Lee's "perfect battle": his forces, less than half the size of the Union forces engaged, drove the Army of the Potomac away. Lee aimed to capitalize on his success in a march into Pennsylvania, which was defeated at Gettysburg in 1863, one of the turning points of the war. Lee returned south. The subsequent Bristoe and Mine Run campaigns of 1863 were unsuccessful attempts by the Army of the Potomac to destroy the Confederate army; the Wilderness campaign of 1864 succeeded in manoeuvring to a siege of Petersburg, threatening the Confederate capital of Richmond. The final campign culminated in Lee's surrender of the Army of Northern Virginia at the Appomattox Court House in 1865. This was essentially the end of the Civil War