As nouns the difference between rei and reg
is that rei is an old Portuguese money of account while reg is a hard surface of rock fragments set in a sandy matrix, found in some hot deserts; regolith, stony desert.
As a proper noun Reg is
a diminutive of the male given name Reginald.
rei
English
Alternative forms
* ree
Noun
(s)
An old Portuguese money of account.
reg
English
Etymology 1
Abbreviation