Notes on criminal gang (5)
I believe the answer is:
triad
This might be a double definition.
'notes on criminal' is the first definition.
I know that 'criminal' relates to this answer. I also know that both the answer and definition are singular nouns
'gang' is the second definition.
(I've seen this before)
Can you help me to learn more?
(Other definitions for triad that I've seen before include "Chinese criminal society" , "Up to date" , "Union of three" , "Chinese secret society" , "Set of three; chord" .)