This paper delves into the meanings of the Modern Greek prefix /ðia/ both in the standard and dialectal uses. The prefix is studied from a synchronic and a diachronic viewpoint. The authors record instances from the Historical Dictionary of Modern Greek (ILNE) and examine the variants/allomorphs of the prefix. The variants are examined in terms of their derivational properties, productivity, their semantic range, and various etymological aspects. It is suggested that the prefix /ðia/ is highly productive in the dialectal area since many derivational patterns of past periods have survived in full function, which, in turn, result in new formations.