"The woman who is speaking is tall."
Translation:Η γυναίκα η οποία μιλάει είναι ψηλή.
Question: In the 'tips and notes' for the relative pronouns lesson it says: "Relative pronouns simply consist of the 3rd person personal pronoun endings, with the prefix οποί- instead of αυτ-." However, the feminine 3rd person personal pronoun would be "αυτή - αυτής - αυτήν" which doesn't correspond with "οποια - οποιας - οποια".
Am I missing something or is it just a mistake in the tips and notes?
After checking, it's not quite all vowels.
- if there's an accented vowel at the end of the stem, then the feminine ends in -α
- if the accent is on the third syllable from the end, then the feminine ends in -α if the adjective ends in -ιος -ειος -οιος -υος (but not e.g. in -αιος, -εος, -οος, -ουος)
- if the accent is on the ending itself (-ός), then I believe the feminine ends in -ά if there is an /i/ sound in front, as with the previous rule.
There are also a handful of other exceptions but those seem to be the main rules.
(Another exception involves rho: adjectives used to end in alpha after rho, but this only survives in some fixed expressions such as the day of the week Δευτέρα, which also has stress shift unlike modern adjectives; the word "second" in feminine form is otherwise δεύτερη.)
So you have e.g. η αρχαία Ελλάδα, η κρύα θάλασσα, η νέα εκκλησία, η τελευταία εβδομάδα, η καινούρια νταλίκα, μια σπάνια εμπειρία, μια τέλεια γυναίκα κτλ.
Like the difference between жена которую + жена которая.
γυναίκα has the case depending on the role in the first sentence, η οποία has the case depending on the role in the second sentence.
They can be the same or different.
For example, Ξέρω τη γυναίκα η οποία τραγουδάει (I know the women who sings -- accusative for τη γυναίκα as object of ξέρω, but nominative for η οποία as subject of τραγουδάει), or Η γυναίκα την οποία συνάντησα είναι πλούσια (the woman whom I met is rich -- nominative for η γυναίκα as subject of είναι πλούσια but την οποία accusative as object of συνάντησα "I met").