A single-hung window is a type of window that features two sashes, or frames, but only one of them is operable. The bottom sash can be raised to allow fresh air in, while the top sash remains fixed in place. This design is popular for its simplicity and ease of use, making it a common choice for residential buildings. These windows are typically more affordable than other styles, such as double-hung windows, where both sashes can move. Single-hung windows are also easier to install and maintain, making them a practical option for homeowners looking for functional and cost-effective window solutions.