Markos wrote:In the word (phrase?) τὄυνεκα, you would have to say that the article is functioning as a prefix.
No, not really, as I understand it. Prefixing is *not* an umbrella term for any combination of words or word parts to make a larger word.
With prefixing, you have a word fragment that can't stand alone (called a bound morpheme) which is added before a word root to make a new word. Many prefixes are derived from adverbs or prepositions, and they'll have a meaning which is in some way related, but they're not, strictly speaking, functioning as prepositions when used this way. (There is a grey area here, as any speaker of German will know or anyone familiar with the Homeric phenomenon of tmesis -- prefixes can go wandering and become separated from their verbs, but they're still not functioning as prepositions because they don't form a prepositional phrase)
In the case of compounding, you have two or more roots (lexemes, really; units that can serve as the basis for a word and which can be inflected or added to to create derivatives) that are being stuck together, sometimes in slightly modified form. Compounds may not be as productive as prefixes, and the meaning or relationship between the parts may not be as easy to predict.
τὄυνεκα is neither of the above. It's an example of a phrase (article + postposition) which has become fossilized and now functions as a single word. A lot of conjunctions are formed this way. One huge difference between something like this and prefixing is that the parts being combined still show inflection and follow the rules of prepositional phrases -- prefixes don't.