Is it ensure, insure, or assure?
An arc-shaped spectrum of color seen in the sky opposite the Sun, especially after rain, caused by the refraction and reflection of sunlight by droplets of water suspended in the air. Secondary rainbows that are larger and paler sometimes appear within the primary arc with the colors reversed (red being inside). These result from two reflections and refractions of a light ray inside a droplet.
The colored arch in the sky that is often seen after a rain. The rainbow is formed when water droplets in the air cause the diffraction of sunlight.
Note: The colors of the rainbow are violet, indigo, blue, green, yellow, orange, and red.
caused by the reflection and refraction of the rays of the sun shining on falling rain. It was appointed as a witness of the divine faithfulness (Gen. 9:12-17). It existed indeed before, but it was then constituted as a sign of the covenant. Others, however (as Delitzsch, Commentary on Pentateuch), think that it "appeared then for the first time in the vault and clouds of heaven." It is argued by those holding this opinion that the atmosphere was differently constituted before the Flood. It is referred to three other times in Scripture (Ezek. 1:27, 28; Rev. 4:1-3; 10:1).