e·co·sys·tem 
(ēkō-sĭs′təm, ĕkō-)
(ēkō-sĭs′təm, ĕkō-)n.
An ecological community together with its environment, functioning as a unit.
- underperformance
- underperformer
- underpin
- underpinning
- underplay
- underplot
- underpopulated
- underpopulation
- underprice
- underprivileged
- underproduce
- underproduction
- underproof
- underprop
- underran
- underrate
- underreact
- underreaction
- underreport
- underrepresent
- underrepresentation
- underrepresented
- underrun
- under sail
- underscore