  We propose novel triangle relations, not the well-known triangle singularity,
for better understanding of the exotic XYZ states. Nine XYZ resonances,
X(3872), Y(4230), Zc(3900), X(4012), Y(4360/4390), Zc(4020), X(4274), Y(4660),
and Zcs(3985) have been classified into triples to construct three triangles
based on the assumption that they are all tetra-quark states. We also suggest
some channels deserving search for with high priority based on this hypothesis,
as well as predictions of a few production/decay rates of these channels. We
hope further experimental studies of the XYZ states will benefit from our
results.
