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).