List of Words for Letter ‘R’

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radiation The transfer of energy through space.
rain gauge A device that measures how much precipitation has fallen.
recycle To make new objects or materials from old objects or materials.
reduce use less of something.
reflection AThe bouncing of light waves off a surface.
refraction The bending of light as it passes from one transparent material into another.
relative age Tage of one thing as compared to another.
renewable resource A useful material that is replaced quickly in nature.
repel To push away.
reproduction The making of offspring.
reptile A cold-blooded vertebrate that has scaly, waterproof skin, breathes air with lungs, and lays eggs.
reservoir storage area for holding and managing fresh water.
resource A material or object that has useful properties.
respiration The using and releasing of energy in a cell.
respiratory system The organ system that brings oxygen to body cells and removes waste gas.
reuse To use something again.
revolution One complete trip around an object in a circular or nearly circular path.
rock cycle The process in which rocks continuously change from one type to another.
root The part of a plant that takes in water and minerals.
root hair One of the threadlike cells on a root that takes in water and minerals.
rotation The act of spinning around an axis.
runoff Water that flows over the surface of the land but does not evaporate or soak into the ground.
rust A solid brown compound formed when iron combines chemically with oxygen.