discern

v.

1. To see

   observe, behold, make out, perceive, notice, espy, descry, recognize, spot; see also see 1.

2. To detect

   discover, distinguish, differentiate, find out, determine, ascertain, judge, apprehend, discriminate; see also discover.

discern implies a making out or recognizing of something visually or mentally to discern one's motives; perceive implies recognition by means of any of the senses, and, with reference to mental apprehension, often implies keen understanding or insight to perceive a change in attitude; distinguish implies perceiving clearly or distinctly by sight, hearing, etc. he distinguished the voices of men down the hall; observe and notice both connote some measure of attentiveness, though the former may imply a more conscious act of will, and both usually suggest use of the sense of sight to observe an eclipse, to notice a sign