Mucilage is a thick, sticky, glue-like substance that many plants produce, especially from their seeds, roots, and stems. When you soak chia seeds or flax seeds in water and they develop that slippery, gel-like coating, that's mucilage. If you've ever broken open an aloe vera leaf and felt that clear, gooey gel inside, you've touched mucilage.

Plants make mucilage for several clever reasons. It helps seeds stay moist and stick to the ground or to animals' fur for transportation. It protects roots by holding water in dry soil. The okra vegetable contains lots of mucilage, which is why it gets slippery when cooked.

The word also refers to a type of adhesive glue used for sticking paper, made to mimic the sticky quality of plant mucilage. Before modern glues and tape became common, bottles of mucilage sat on school desks and in offices for attaching papers together. These old-fashioned glues often came with a rubber applicator attached to the cap.

Though the word sounds like something from a science fiction movie, mucilage is an ordinary part of nature that you may encounter more often than you might think.