{acy} acyclic atom
{scy} atom belongs on at least one cycle
{dcy} atom belongs on two or more cycles
{sscy} strict single cycle. System search chemicals with single cycles only
{sp1} hybridization
{sp2} hybridization
{sp3} hybridization
{ar} aromatic atom
{Vx} where x is a digit . valencies of the atom
{n+} where n is a digit . positive charge
{n-} where n is a digit . negative charge
{.} mark radical atoms
{*} mark specific atom of interest (e.g for calculations of Q)