subordinate vs vassal

To make subservient. 

To treat as of less value or importance. 

To make of lower priority in order of payment in bankruptcy. 

Descending in a regular series. 

Placed in a lower class, rank, or position. 

dependent on and either modifying or complementing the main clause 

Submissive or inferior to, or controlled by authority. 

To subordinate to someone or something. 

To treat as a vassal or to reduce to the position of a vassal; to subject to control; to enslave. 

The grantee of a fief, a subordinate granted use of a superior's land and its income in exchange for vows of fidelity and homage and (typically) military service. 

Any subordinate bound by similar close ties. 

Any direct subordinate bound by such vows to a superior.