interplay /inˈtər-plā/

1. Mutual action
2. Interchange of action and reaction

• ultra-tropical
• ultraviolet
• ultraviolet microscope
• ultraviolet spectroscopies
• ultraviolet spectroscopy
• ultraviolet star
• ultraviolet stars
• ultra vires
• ultra-virtuous
• ultroneous
• ultroneously
• ultroneousness
• ultroneousnesses
• ululant
• ululate
• ululated
• ululates
• ululating
• ululation
• ululations
• ulva
• ulvas
• ulyie
• ulzie
• um