* Adjective: This is the most common usage. It describes something clear, easy to understand, or mentally sound.
* Example: "The professor gave a lucid explanation of the complex theory."
* Noun: While less common, "lucid" can also be used as a noun to refer to a period of mental clarity, especially during a dream or illness.
* Example: "She had a lucid dream about her childhood home."
Therefore, the part of speech for "lucid" depends on its context within a sentence.