Simplify the following text for a Grade 8 native English-speaking person.
Original: Mu ( uppercase\/lowercase Î Î 1\/4 ) , is the letter of the Greek alphabet , used to represent the `` m '' sound in Ancient and Modern Greek .
Simplified: Mu ( uppercase Î , lowercase Î 1\/4 ; Ancient Greek ) , Modern Greek Î 1\/4 Î or Î 1\/4 Ï