refer to two groups of people:
1) the ancient hellenes
2) modern greeks
unbeknownst or outright denied by "modern" greeks, there isn't really any relation racially between the hellenes and the "moderns". the slavic migrations between 600-800ad completely overwhelmed greece. the population of greece has always been small, even moreso during those times. constant warfare depleted the population further. the slavs managed to settle thessaly,aetolia,macedonia,thrace and the
peloponesos. virtually every major part of greece, save for boeotia(which is where dislocated albanians settled)was overrun by the slavs. to this day there are still towns with slavic etymology. the "greeks" of today are nothing more than the descendants of hellenized slavs, which was the policy of the church to gain converts, and of the byzantine empire in order to free itself from a two front war against eastern armies of islamic faith. the gene pool of the hellenes, while not completely decimated was absorbed by the slavs.
the slavs were classified as greek speaking, slav speaking, or bulgarian speaking. through the years other ethnicities were thrown into the mix: normans,venetians,romanians,turks egyptians. modern day peoples of the balkans have varying degrees of the admixture of these ethnicities, and the "greeks" are no exception.
it is foolish of the greeks to believe they are directly descended from the ancient hellenes.