Sentence:  &#91;[https://books.google.com/books?id=GBZMAAAAYAAJ&pg=PA115 page 115]&#93; The truth is, "we discover no trace of a "Sabbath"" even among those oriental nations which had the <WSD>"hebdomade</WSD>" or week: but to the Greeks, "the week itself was unknown"!—their smallest interval being the "decade" or period of ten days. [...] &#91;[https://books.google.com/books?id=GBZMAAAAYAAJ&pg=PA121 page 121]&#93; Making due allowance for the natural exaggeration of an apologist, the substance of this statement expresses a well-recognized fact in Roman history. "The institution of the <WSD>Hebdomade</WSD>" (introduced about the date of the Christian era) "did" travel almost throughout the empire. 
Meaning of the word marked with <WSD> tags:  A period of seven days; a week.