- underdetermined linear system
- underdetermined system
- underdetermined system of equations
- underdevelopment
- underdoped regime
- underdoping
- underdot
- underestimate algorithm
- underexposure
- underfitting
- underfloor air distribution
- underflow
- underflow tube
- under fly
- underfocus
- under-forest economy
- under fur
- underglaze blue
- underglaze dark blue glaze
- underglaze dark blue glazed
- underglaze decoration
- underglaze red
- undergoing professional training at an old-type opera school
- undergraduate education
- undergraduate education of pratacultural science