From the Greek noun οἶκος (oíkos), meaning "house," and the word λόγος (lógos), meaning "reason, consideration, reckoning," ecology is a term first coined in 1866 as Ökologie by the German scientist Ernst Haeckel. Ecology is "the branch of biology that deals with the relations of organisms to one another and to their physical surroundings"—literally the study of organisms to their "houses."