Greek alphabet
Although the Greek letters accurately represented all the main sounds of the Greek language early on, the sounds of the Greek language changed over time. Some of the vowel sounds began to sound similar to one another, aspirated voiceless stops became voiceless fricatives, and voiced stops became voiced fricatives. One can get an idea of how older Greek pronunciations sounded, by looking at the Latin and English spellings of Greek loanwords like "philosopher", "Chimera", "Cyprus", and "Thessalonica".