Page "English orthography" Paragraph 7

Another type of spelling characteristic is related to word origin.

For example, when representing a vowel, the letter ⟨ y ⟩ in non-word-final positions, represents the sound in some words borrowed from Greek ( reflecting an original upsilon ), whereas the letter usually representing this sound in non-Greek words is the letter ⟨ i ⟩.

Thus, the word myth is of Greek origin, while pith is a Germanic word.

Other examples include ⟨ ph ⟩ pronounced ( which is usually spelt ⟨ f ⟩), and ⟨ ch ⟩ pronounced ( which is usually spelt ⟨ c ⟩ or ⟨ k ⟩) – the use of these spellings for these sounds often mark words that have been borrowed from Greek.