What is thereupon? How to use in English

The origin of the word "thereupon" can be traced back to Middle English, a language spoken in England from the 11th to the 15th centuries. The Middle English word "ther" (meaning "then" or "there") was often combined with the preposition "on" (meaning "upon") to create a new word. In its early form, "theron" was used primarily in legal documents and administrative writings to signify the immediate result or consequence of an action or event. The word's original meaning also included a spatial sense, implying movement or advancement. Over time, "theron" fell out of use in favor of simpler and more widely understood phrases like "thereafter" and "subsequently." However, it reemerged in the 16th century with a renewed sense, now primarily used as a conjunction to express cause and effect. The modern form of the word, "thereupon," is a result of evolving grammatical rules. Today, "thereupon" is a marginalized and infrequently used word, seen primarily in formal or archaic English, but its history underscores the evolution of the English language and the way that words can change meaning and usage over time.