lichen

"Astronomers study symbiotic stars to understand how two stars can orbit each other and exchange matter. "

"My friend told me there was something in the box, but I didn't know what it was yet. "

"Children grow quickly."

"The plants gradually grew taller over the summer. "

"The old stone wall was covered in patches of green, gray, and yellow lichens. "

"His sleeves had patches on the elbows where different fabric had been sewn on to replace material that had worn away."

"The foster parents fostered the child for several years, providing a loving home and support. "

"The family kept their old bicycles in the basement. "

"The dampness in the basement made the floorboards squeak. "

"The child's associations with the park were mostly happy, filled with memories of playing with friends. "

"Be careful not to damage any of the fragile items while unpacking them."

"Scientists study different organisms, such as bacteria and plants, to learn about life on Earth. "