The accent mark ΄ indicates which syllable is stressed in a word. The accent mark is not written over one -syllable words, except for question words (πού & πώς), conjunction ή and preposition ώς.
When the stressed syllable is one of the two- letter vowels αι, ου, ει, οι one of the combinations αυ or ευ, the accent mark goes over the second letter of the combination : είναι, γυναίκα, είμαι.
The mark ¨ is used to indicate that the vowels of an unstressed two-letter vowels or combination are pronounced separately e.g. τρόλεϊ
You can also read: Cases and syntactic functions
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