In North America, it is referred to as lumber, while in other countries it is usually called timber.
2 x 4’s are a popular cut of wood which is normally used for home and business construction.
The weight of a 2 x 4 will depend on a number of factors including the length of the wood, the type of wood, and whether it is treated or not.
Average 2×4 Weights
Green Boards
8 foot – 13 pounds (5.89 kg)
12 foot – 20 pounds (9.07 kg)
Pressure Treated
8 foot – 17 pounds (7.71 kg)
12 foot – 26 pounds (11.79 kg)
~ Fun Fact ~
A British oak tree can live for 500 years.
Resources
https://www.familyhandyman.com/carpentry/making-sense-of-lumber-dimensions-like-2×4-dimensions/view-all/
https://www.engineeringtoolbox.com/green-kiln-dried-pressure-treated-lumber-weights-d_1860.html