These words describe someone with a sharp eye for detail or a keen ability to detect the real meaning of a situation. Observant suggests someone who notices details that another person might miss: Only the most observant spectator would have seen which player was offside. Discerning and perceptive take in this emphasis of observant , but add to it an ability to evaluate or understand the observed details. Discerning stresses the ability to tell apart two or more very similar things – or to evaluate slight differences by means of one’s inherent good taste: the discerning theatregoer who shuns bad imitations of last year’s successes. Perceptive stresses that ability to understand or make understandable the details one has observed: a perceptive comment on campaigns needed to combat juvenile delinquency.

Attentive resembles observant more than discerning and perceptive ; it stresses the ability to concentrate on a matter without distraction or wavering of any kind: students who suddenly become attentive the week before exams; members of Parliament who are attentive to the needs of their constituents. Aware and alert also resemble observant , but they are more general than the other words here. In a different context, aware can point merely to being conscious; here it suggests acute responsiveness to other people or to one’s surroundings: discussing how they could become more aware of each other’s problems. Alert is similar to, but an intensification of, aware ; it suggests a sharp, highly receptive state of mind that is on the look-out for some event to occur, especially a dangerous or threatening event: so alert that not a single error in the report slipped past her; alert for any sign of change in the critically ill patient.