so, I see that if I translated this Greek sentence to my language ( French) I cannot translate it like you do in English. Since TOU is the genitive of TO, it means OF THE in English and DU or DE LA in French. This is why i make mistakes in English. I said " the parts of the speech" because it is exactly what it says ( gramaticallky speaking ) in Greek too. In French i cannot translate other than " les parties DU discours" i.e. " the parts OF THE speech " O THEOU PHOBOS IS ALETHEIA TES SOPHIAS. = The fear OF God is the beginning OF THE wisdom". ( La crainte DE Dieu est le commencement DE LA sagesse ) just to emphasize the use of the genitive case in this sentence. nothing to do with religion, just old memories of my students days 60 odd years ago.! have a nice day.
In this skill we are discussing "the parts of speech" which refer to the grammatical items used in a language...article, nouns, verb etc.
But we can also use "speech" as in "The award winner gave a speech to the audience." There you can use "The parts of a speech."
But that doesn'w work here because theGreek doesn't hav "a".