Filling (noun)

1. A substance used to fill a cavity or space.
2. A food that is used to fill a pastry, sandwich or baked good.
3. Something that fills a gap or fulfills a need.
4. An added ingredient that provides flavor, texture, or nutrition.

Origin:

Derived from the old english word 'fylian', which means 'to fill'.

Examples:

1. The dentist used a filling to repair the cavity in my tooth.
2. Chocolate is a popular filling for donuts.
3. Her promotion to manager filled the vacancy that was created when the previous manager resigned.
4. The company added a new product to its line-up to fill a gap in the market.
5. The fruit filling in the pie was the perfect addition to the crust.