Subsidiary

Etymology

From Latin "subsidiarius" (belonging to a reserve), from "subsidium" (support, or reserve troops held in the rear). The military reserve — a force standing behind the front line — became the sense of something supporting a larger body. A subsidiary is, in effect, a company held under and in support of its parent.

noun · /sub-SID-ee-air-ee/
A company that is owned or controlled by another, larger company.
What it names
The corporate child that runs semi-independently while the parent keeps control, explaining why familiar brands share hidden ownership.
Example
The airline was actually a subsidiary, wholly owned by a holding company most travelers had never heard of.
Related idea
A subsidiary is a controlled company; a conglomerate is a parent that owns many, often across unrelated fields. Ownership is the link: several subsidiaries under one diverse parent make a conglomerate.
adjective · /sub-SID-ee-air-ee/
Less important than something else; serving in a supporting or secondary role.
What it names
a supplementary part, aim, or detail.
Example
That’s a subsidiary concern — focus on the main goal.
Related idea
The company sense is this adjective made a noun: a business kept in a supporting, controlled position.