  Exploring structural order in disordered systems including liquids and
glasses is an intriguing but challenging issue in condensed matter physics.
Here we construct a new parameter based on the angular distribution function of
particles and show that this new orientational order has significantly higher
correlation with dynamic heterogeneity compared to a translational parameter
based on the radial distribution functions in colloidal glasses. The gradual
development of orientational and translational order in supercooled liquids
shows that the higher correlation between orientational order and dynamics
comes from the onset of glass transition and the orientational order would
dominate the glassy dynamics after a simple liquid is considerably supercooled.
Our results suggest that orientational order reflects the formation of
amorphous order during glass transition while translational order is mainly a
result of density increase.
