noun
lining
LY-ning/ˈlaɪnɪŋ/
a layer covering the inside of something
The jacket opens to reveal a contrasting fabric lining.

Etymology
Linen cloth was used as an inner layer in garments, giving rise to the verb meaning “cover the inside.” Lining then broadened from garment material to any inner covering.
In context
this nice shiny watertight airtight lining to the thoracic cage and that's the parietal pleura
More examples
- She repaired a tear in the pocket lining.
- A smooth lining protected the jewelry inside the box.
- The bag's lining was made from cotton.
Forms
lining · linings
Similar words
- liner
- Often a separate removable protective layer.
- padding
- Provides cushioning rather than merely covering the inside.