What is the term for the load-carrying member over a door or window?

The term for the load-carrying member over a door or window is "header." A header is specifically designed to span openings and support the weight of the structure above it, such as walls or roof loads. It is a critical component in framing as it ensures that the weight is properly distributed and does not cause structural failure around the opening.

While "beam" can refer to a horizontal support that carries loads in various applications, it is a more general term and may not specifically denote the component used at door or window openings. "Lintel" is sometimes used interchangeably with header in different regions or contexts, but it traditionally refers to a structural member that spans an opening, often carrying loads from above but can imply a different material or application. "Truss" refers to a structural framework used to support roofs and other structures, not specifically associated with openings like doors or windows. Thus, "header" is the most accurate and commonly used term for this specific application in carpentry and construction.