"This word is an adjective."
Translation:Αυτή η λέξη είναι επίθετο.
Okay first things first. Λόγος generally translates to speech, (parts of speech, μέρη του λόγου), or reason. It does translate to word too, but these cases are really few (its use is almost idiomatic.) And this case is not one of them.
As far as the articles go, ο λόγος is masculine, so the sentence would have to be "Αυτός ο λόγος....", (you know... if that actually worked.:P)
I hope I'm clear enough ^.^