Definition of lucid

The word "lucid" comes from the Latin word "lux," meaning light, and "cidus," meaning clear or transparent. Together, "lucidus" translates to "clear like light" in Old Latin. The term lucidus was used to describe anything that was shining or brilliantly clear, from the shine on a person's head to the clarity of the moon in the sky. Later, the Latin word evolved to describe complex ideas, such as the lucidity of ancient Greek philosophers' arguments, as they presented their ideas with absolute clarity and distinctness. In medieval Latin, the term "lucidus" came to be associated with the clarity of a person's thinking, as opposed to their general knowledge. Latin learners in this period used the word to describe someone who think discerningly, as in the phrase "lucidus ingenii" (shining intellect). In modern English, this same philosophical and cognitive meaning is still conveyed by the word "lucid." Today, "lucidity" signifies the ability to think and communicate clearly, in stark contrast to the more associated word "delirium," which refers to confused or distorted thinking.