TEU is an acronym for Twenty Foot Equivalent Unit. FEU is an acronym for Forty Foot Equivalent Unit. 

Both are used to describe the size of a container. They’re also used as a measure to standardize the amount of volume being referenced.  For example, if an importer shipped 2 x 20FT containers and 1 x 40FT container this week, she could say that she shipped 4 TEU or 2 FEU.  

Containers larger than a standard 40FT, such as a 40HC, 45HC, 48HC or 53HC, would referenced as 2 TEU, 2.25 TEU, 2.4 TEU, and 2.65 TEU respectively.