Ginger is considered a stem rather than a root due to the following characteristics:
$1$. Presence of Nodes and Internodes: Ginger possesses distinct nodes and internodes,which are characteristic features of a stem. Roots do not have nodes or internodes.
$2$. Presence of Buds: The nodes of ginger bear buds (axillary buds),which can give rise to new aerial shoots. Roots lack such buds.
$3$. Adventitious Roots: The roots seen growing from the ginger rhizome are adventitious roots,which arise from the nodes of the stem,not from the radicle.
$4$. Function: While roots are primarily involved in anchorage and absorption,the ginger rhizome functions as a storage organ for food,which is a common modification of underground stems.