instruction:
In this task, we ask you to rewrite a sentence in simple English without changing its general meaning. Essentially, you want to make the sentence easier to read by using simpler words, utilizing more straightforward sentence structures, and omitting non-essential information etc.
question:
The Pentagon is the headquarters building of the United States Department of Defense , although as a symbol of the U.S. military , the phrase " The Pentagon " is also often used as a metonym for the Department of Defense and its leadership .
answer:
The Pentagon is the headquarters of the United States Department of Defense .

question:
It was common for the Ernestine duchies to merge and split ; Ernest 's combined duchy was divided again after his death in 1675 , and the Duchy of Saxe-Gotha-Altenburg proper came into existence in 1680 with the completion of this division and the accession of his eldest son , Frederick to the subdivision centered on the towns of Gotha and Altenburg .
answer:
The duchy was split up again after Ernest ' s death in 1675 , and the Duchy of Saxe-Gotha-Altenburg officially came into existence in 1680 when his eldest son , Frederick , took control of the parts of the country Gotha and Altenburg .

question:
The University of California , San Diego ( UC San Diego , or colloquially , UCSD ) is a public research university located in the La Jolla neighborhood of San Diego , California , in the United States .
answer:
The University of California , San Diego ( UCSD or UC San Diego ) is a public research university .