A diphthong is a combination of two vowel sounds in a single syllable. In Greek, they may be written with an umlaut on the second vowel or an acute accent on the first vowel.

Greek has two different accents: acute (ί) and umlaut (ϊ). The acute accent is far more common and has two main uses.

Three consonants (κ, γ, χ) and two double consonants (γκ and γγ) have different pronunciations depending on the vowel that follows.

Greek has seven vowels (letters) for just four vowel sounds. There are also eight double vowels: one creates a fifth vowel sound, four are alternate spellings for regular vowels, and three make a vowel + consonant sound.

Greek has 17 consonants (letters), most of which are similar to English sounds. There are also six double consonants.

The Greek alphabet has 24 letters. Some have no real English counterpart, and several have misleading English names.