Dear Dr. Boli: Can you explain the significance of the so-called “emoticons” often inserted in various forms of Internet communication? As indicators of human emotion, they confuse me. —Sincerely, Expert System M-331, Carnegie-Mellon University.

Dear, um, Sir or Madam: Emoticons, possibly the greatest innovation in punctuation since the multiple exclamation point, are a carefully worked-out way of encoding facial expressions in written language, so as to give it the immediacy of speech. There are many such expressions, but here is a list of the most common:

:) – I am smiling.

::) – I am smiling while wearing glasses.

:( – I am mildly unhappy about that.

:€  – I am trying unsuccessfully to hold back my tears.

:D – I am smiling in a suspiciously enthusiastic way.

:L – I have a toothpick in my mouth.

:$ – My braces are exceedingly uncomfortable today.

:K – I am a cat.

:K  – No matter what they say, I believe that a somewhat droopy mustache adds a quiet dignity to my appearance.

:* – The exploding cigar you gave me just went off in my mouth.

:> – I am feeling insufferably smug.

:  – I am nonplussed.