The term "september 11th birthstone" functions grammatically as a noun phrase. In this construction, the word "birthstone" is the head noun, which is the central element of the phrase. The terms "september" and "11th" act as adjectival modifiers, specifying the particular birthstone in question by linking it to a specific calendar date. Therefore, the phrase as a whole names a singular concept: the gemstone associated with birth on the eleventh day of September.
Birthstones are traditionally assigned to calendar months rather than to individual days. Consequently, the gemstone for September 11th is the same as that for the entire month of September. The primary and most widely recognized birthstone for September is the Sapphire. A variety of the mineral corundum, sapphire is renowned for its deep blue color, although it occurs in a full spectrum of colors known as "fancy sapphires," excluding red, which is classified as ruby. Lapis Lazuli is also sometimes cited as a secondary or alternative birthstone for this month.
In practical application, an individual born on September 11th would claim the Sapphire as their designated birthstone. This gem historically symbolizes wisdom, virtue, and good fortune. Understanding the grammatical function of the keyword as a noun phrase is crucial because it frames the subject as a specific entity to be defined. The definition is derived not from the day itself but from the established gemological association with the month of September.
