As computer monitors are getting bigger and bigger, we do not abbreviate names, except for the cases below.
Abbreviations used in the field:
rep for representation, as is customary in the field
irrep for irreducible representation, same
Abbreviations from Matlab (or toolboxes) conventions:
conj for conjugate
n for number
nCopies for numberOfCopies
nXYZ for numberOfXYZ
fun for function
var for variable (YALMIP)
str for string
Other abbreviations:
eqv for equivalent
col(s) for column(s)