Supplementary (adjective)

1. Providing additional information or resources.
2. Intended to supplement or complement something else.
3. Added to complete or make something more effective.

Origin:

From the latin word "supplementum" meaning an addition or something added.

Examples:

1. The supplementary materials provided additional information on the topic.
2. The company offered a supplementary health insurance plan to its employees.
3. The teacher gave us a supplementary reading list.
4. The supplementary budget was passed to cover the additional expenses.
5. The supplementary oxygen helped her breathe better.