{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)