What is the origin of 'sleep tight'?
Read moreOne of the mysteries of the English language finally explained.
A yellow, crystalline, heteroaromatic compound with a bicyclic molecular structure; any substituted derivative of this, many examples of which occur naturally, especially as insect pigments and vitamins of the B group. Compare earlier pterin.
1940s. From pter- + -idine, after German Pteridin.