【Subordinate】 ,  【secondary】 ,  【dependent】 ,  【subject】 ,  【tributary】 ,  【collateral】  are comparable when they mean placed in or belonging to a class, rank, or status lower than the highest or the first in importance or power.

【Subordinate】 applies to a person or thing that is lower than another in some such essential respect as by being under his or its authority or by having a less important or less conspicuous place, position, or status in the scheme of a whole than some other member, part, or element or by loss of independence and reduction to a lower or inferior position.

【Secondary】  differs from  【subordinate】  mainly in suggesting a much narrower range of difference, for it implies a position or an importance that is just below what may be described as primary , main , chief , or leading .

In reference to order of development or derivation  【secondary】  is opposed to original or first and carries no necessary implication of inferiority in importance.

【Dependent】  (see also  【DEPENDENT】 1 ) implies subordination to someone or something, but it also connotes the position or the status of one that hangs on, leans on, or relies on the other for support or for the provision of what is lacking in itself; thus, a  【dependent】  clause in a sentence is not completely intelligible apart from the main clause; a  【dependent】  child is not old enough to support himself and therefore must rely upon his parents or guardians. In its commonest use  【dependent】 implies a loss, through subjugation or through weakness, of one’s independence; it therefore frequently stresses powerlessness or debasement more than subordination.

【Subject】  definitely implies subordination to a dominant power but never carries, as  【subordinate】 sometimes carries, an implication of relative importance within a scheme of the whole; it often tends to suggest loss of those powers which imply a degree of freedom, responsibility, self-discipline, and self-sufficiency.

【Tributary】  basically applies to peoples, races, or nations that have been conquered and made 【subject】 to another people, race, or nation and that are forced to pay tribute to their conquerors, but in more general use it is often interchangeable with  【subject】 .

In another sense it is also applicable to whatever has an outlet into another and larger thing of the same kind and thereby yields supplies (as a flow of water or material) which increase the size or importance of the latter.

【Collateral】  implies a being side by side, but it suggests not equivalence in value but subordination of one through or as if through an indirect relation to or a loose connection with the other; thus, a  【collateral】  cause of a war, though by implication operative at the same time as the most important or primary cause, is 【subordinate】 to the latter; a  【collateral】  issue is not the main issue; a  【collateral】 descendant is not a direct or lineal descendant but one in a different line (as of a brother or sister).