Mahogany has higher density compared to elm. This is due to several factors that contribute to the physical properties of these woods. Mahogany, scientifically known as Swietenia macrophylla, is a tropical hardwood that is renowned for its dense and heavy nature. Elm, on the other hand, is a deciduous tree that produces a lighter wood with a lower density.

The density of wood is a measure of its mass per unit volume and is typically expressed in pounds per cubic foot (lb/ft³) or kilograms per cubic meter (kg/m³). According to the Wood Database, the average density of mahogany ranges from 45 to 52 lb/ft³, whereas the density of elm wood varies between 35 to 40 lb/ft³. This significant difference in density is attributed to the composition and structure of the wood cells.

Mahogany wood has a higher density because it contains more wood fibers and a denser cell structure. The fibers in mahogany are tightly packed and oriented in a manner that enhances the wood's strength and durability. Elm wood, while still strong and versatile, has a more open cell structure, which results in a lower density. This difference in cell structure is also reflected in the wood's grain pattern, with mahogany typically having a straight grain that contributes to its strength and rigidity.

The higher density of mahogany makes it more suitable for applications that require a strong and durable material, such as furniture construction, boat building, and musical instruments. Elm wood, while lighter and more flexible, is often used for furniture, cabinetry, and veneers. The density of elm wood can also vary depending on the species, with white elm and red elm having slightly different densities.

In conclusion, mahogany has a higher density than elm due to its dense cell structure and higher concentration of wood fibers. This difference in density is a key factor in determining the suitability of each wood type for various applications.