List of Words for Letter ‘R’

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radial symmetry A body plan in which all body parts of an organism are arranged around a central point.
radiation The transfer of heat through electromagnetic rays.
rain shadow The dry area on the leeward side of a mountain.
reactant original substance at the beginning of a chemical reaction.
reaction force The push or pull of a second object back on the object that started the push or pull.
recessive trait The form of a trait that is hidden, or masked, in the hybrid generation.
refraction The bending of waves as they pass from one substance into another.
relative age The age of one rock or fossil as compared to another.
relief map A map that shows the elevation of an area using colors or shading.
renewable resource A resource that can be replanted or replaced naturally in a short period of time.
reservoir A storage area for fresh water.
resistor An object in an electrical circuit that resists the flow of electrons.
respiratory system The organ system that brings oxygen to body cells and removes waste gas.
revolution One complete trip of one object around another object.
rock cycle A never-ending process in which rocks change from one kind into another.
rotation A complete spin on an axis.
runnerPrecipitation that flows across the land’s surface or falls into rivers and streams.
runoff Precipitation that flows across the land’s surface or falls into rivers and streams.