A verb is a string.
The verb is one of the parts of a message or a method signature; in other languages it might be called the "method name" or "selector". Ordinary E objects dispatch to methods based on the combination of the verb and the arity, the number of arguments; this combination is conventionally written “verb/arity” (e.g. “add/1”) and when used in a program is known as a mangled verb or mverb.
def Verb := String