In botany, a perennial plant or simply perennial is a plant that lives more than two years. The term is often used to differentiate a plant from shorter-lived annuals and biennials. The term is also widely used to distinguish plants with little or no woody growth from trees and shrubs, which are also technically perennials. Notably, it is estimated that 94% of plant species fall under the category of perennials, underscoring the prevalence of plants with lifespans exceeding two years in the botanical world.

The term subshrub or undershrub refers to either a small shrub or a perennial that is largely herbaceous but slightly woody at the base. "Subshrub" is often used interchangeably with "bush".