δοῦλος is the usual word for slave, one who is permanently in servitude, in subjection to a master. θεράπων is simply one who renders service at a particular time, sometimes as a slave, more often as a freeman, who renders voluntary service prompted by duty or love. It denotes one who serves, in his relation to a person. διάκονος also may designate either a slave or a freeman, it denotes a servant viewed in relation to his work. οἰκέτης designates a slave, sometimes being practically equivalent to δοῦλος. Usually, however, as the etymology of the term indicates, it means a slave as a member of the household, not emphasizing the servile idea, but rather the relation which would tend to mitigate the severity of his condition. ὑπηρέτης means literally an under-rower, and was used to describe an ordinary rower on a war-galley. It is then used, as in the N.T., to indicate any man, not a slave, who served in a subordinate position under a superior.