Question: is igh a vowel digraph?
Answer: The correct terminology for 2 vowels working together to represent one sound is 'vowel digraph'. The letters 'y', 'w', 'gh' and 'r' are also used in representations of vowel sounds (as in 'ay', 'ow', 'igh' and 'er'), so I quite like using the term 'vowel teams' with younger students.