A handkerchief is a small piece of fabric that people use for wiping their nose or other parts of their face.
Leaves grow all over most plants. Leaves are always some shade of green, although they often have yellow or red patterns on them. Plants use sunlight falling on the green in their leaves, called chlorophyll, to convert air and water into food.
When many coral colonies grow close together over a very long time, they build up to form a reef. Reefs can get so high they come out of the water at low tide, and can be dangerous to ships.