老弟

(affectionate form of address for a male who is not very much younger than oneself) my boy / old pal

prefix used before the surname of a person or a numeral indicating the order of birth of the children in a family or to indicate affection or familiarity / old (of people) / venerable (person) / experienced / of long standing / always / all the time / of the past / very / outdated / (of meat etc) tough

younger brother / junior male / I (modest word in letter)

variant of 悌[ti4]