if You meant to ask r or TM in commerce terms...then the answer is r for registered and TM for trademark

tr does not have any meaning but can be used for postal codes

r=0,


Tr-r = 0 = r(T-1), since T != 1, then T-1 is non zero so r must be zero.

According to SOWPODS (the combination of Scrabble dictionaries used around the world) there are 2 words with the pattern TR--S-R. That is, seven letter words with 1st letter T and 2nd letter R and 5th letter S and 7th letter R. In alphabetical order, they are:

trouser

trusser

not sure if that's even English.