subsidiary

adjective

Pronunciation: /sʌbˈsɪ.di.əɹ.i/ / /sʌbˈsɪ.dəɹ.i/ / /sʌbˈsɪ.d͡ʒəɹ.i/

Etymology: From Middle French subsidiaire, from Latin subsidiarius (“belonging to a reserve”).

Auxiliary or supplemental.
“chief ruler and principal head everywhere, not suffragant and subsidiary”
“They constituted a useful subsidiary testimony of another state of existence.”
Secondary or subordinate.
“a subsidiary stream”
“By one o'clock the place was choc-a-bloc. […] The restaurant was packed, and the promenade between the two main courts and the subsidiary courts was thronged with healthy-looking youngish people, drawn to the Mecca of tennis from all parts of the country.”
Of or relating to a subsidy.
“subsidiary payments to an ally”
“George the Second relied on his subsidiary treaties.”

Etymology: From Middle French subsidiaire, from Latin subsidiarius (“belonging to a reserve”).

A company owned by a parent company or a holding company, also called daughter company or sister company.
A subordinate theme.
One who aids or supplies; an assistant.