ETYM Latin subsidiarius: cf. French subsidiaire. Related to Subsidy.
1. Furnishing aid; assisting; auxiliary.
2. Of or pertaining to a subsidy; constituting a subsidy; being a part of, or of the nature of, a subsidy.

1. Secondary; of lesser importance
2. Furnishing aid; assisting; auxiliary; helping
3. Of or pertaining to a subsidy; constituting a subsidy; being a part of, or of the nature of, a subsidy

In business, a company that is legally controlled by another company having 50% or more of its shares.
A parent company may believe that having a subsidiary is preferable to full integration for taxation purposes, or may allow local participation if the subsidiary is in another country.