molecular

Molecular is an adjective used to describe phenomena, structures, and processes related to molecules—the smallest units of chemical substances that retain the properties of those substances. A molecule is formed when two or more atoms join by covalent or ionic interactions; common examples include water (H2O), oxygen (O2), and methane (CH4).

The term derives from Latin molecula, a diminutive of moles meaning mass, and entered modern chemistry in the 19th century to distinguish molecular-level descriptions from macroscopic ones.

In chemistry, molecular concepts underpin the definition of formulas, structures, and bonding. Molecules may be diatomic or polyatomic and can exhibit isomerism, polarity, and various geometries. The molecular scale is typically in the nanometer range and governs the properties of substances.

Fields focusing on molecular phenomena include molecular biology, which studies biological activity at the molecular level; molecular pharmacology, and molecular genetics. Techniques such as PCR, DNA sequencing, X-ray crystallography, nuclear magnetic resonance, and cryo-electron microscopy reveal molecular structure and function.

Computational chemistry and molecular modeling simulate molecular interactions, while molecular dynamics and quantum chemistry aid drug design and materials research. In cuisine, molecular gastronomy applies chemical principles to cooking, exploring how molecular changes influence flavor, texture, and appearance.