Clear English - Strange Spelling and Pronunciation Items - Page 3
rh The RH combination generally gets pronounced as an R with the H being silent.
  1. This is true in such words as rhythm, thyme, rhyme and arrhythmia.
  2. But why rhythm gets pronounced as rith-them is anyone's guess.
gh This combination of letters has some very varied sets of pronunciations.
  1. In words such as laugh, tough, trough, enough, trough, and cough the GH gets a pronunciation of an F.
  2. In other words the GH is silent: Such as: taught, caught, sought, bought, wrought, ought, fought, haughty, naught, fight, sight, light, might, right, blight, bough, plough, dough, though, borough, furlough, and others.
  3. In some words the H in GH is silent. Such as ghost, ghoul, ghastly, afghan, Ghana, ugh, sorghum, yoghurt, and others.