Japanese bows can be formally categorized as eshaku, a simple 15-degree bend or nod of the head; keirei, a 30-degree tilt to show respect; saikeirei, a full 45- to 90-degree bow intended to show the deepest veneration or humility; and dogeza, a fetal prostration expressing utter subjection or contrition.
But it’s not just the gradient of the bows either.
As important are the duration of the gesture, and the exact context under which it’s made. A graduating student might perform a full, prolonged saikeirei to his professor as a gesture of gratitude, but he might perform the same bow in an abbreviated form to apologize for having accidentally stepped on someone’s foot.
Now taking it to the nth degree, because this is Japan we are talking about.
Bowing is so important in Japan that parents begin to teach the practice to children shortly after they start walking, and some schools hold enormous assemblies where preteens spend hours bowing in unison to master the postures. One company supposedly developed a machine with a laser line to teach their sales staff the ideal angle for bowing to customers.
But really, it’s what those bows signify in the Japanese context that’s both mind-baffling and strangely fitting at the same time.
Still, in most daily interactions, the four categories and the precise pitch of the body matter far less than properly representing the hierarchical relationship between the two parties: The subordinate person—student, son, employee, etc.—must always must bow down lower, and stay there longer, than his superior.