  By doubling the target space of a canonical Courant algebroid and
subsequently projecting down to a specific subbundle, we identify the data of
double field theory (DFT) and hence define its algebroid structure. We specify
the properties of the DFT algebroid. We show that one of the Courant algebroid
properties plays the role of the strong constraint in the context of DFT. The
DFT algebroid is a special example when properties of a Courant algebroid are
relaxed in a specific and dependent manner. When otherwise, we uncover
additional structures.
