Compounds are substances made of two or more different elements joined together. These elements are combined in fixed amounts to form a new substance. Examples include water (H₂O) and carbon dioxide (CO₂). Compounds can exist as solids, liquids, or gases.

Compounds are found in both living and non-living things, such as plants, air, and minerals. They are present in many natural and human-made materials. Each compound has its own properties that are different from the elements that form it.

Compounds are different from mixtures because the elements are joined together. They are part of many substances used in science and daily life. Compounds are common in environments on Earth and beyond.