The phrase "added a major" is correct and usable in written English.
It can be used when discussing changes in academic programs, particularly when a student is declaring or changing their field of study.
Example: "After much consideration, I decided to transfer to a different university where I added a major in environmental science."
Alternatives: "declared a major" or "changed my major".
The Devils added a major weapon when center Adam Henrique joined the lineup for the first time this season.
"In this cycle, we've added a major monkey wrench called electrical power on the West Coast," said Lloyd O'Carroll, an analyst at BB&T Capital Markets.
When the clamor dies down, it will be seen that the Brooklyn Museum is a living institution that has added a major new work to its collection.
When he became impatient with discussions about ideal worlds and hypothetical situations, he added a major in cognitive science so that he could study the real-world workings of the brain.
In October, Jamestown Settlement added a major 30,000-square-foot exhibition hall to its new visitors' center, telling an unusually detailed history of the area through the 17th century.
The president's change of position added a major new twist to the suspicious death of the prosecutor, Alberto Nisman, whose body was found in his luxury apartment in Buenos Aires late Sunday with a fatal gunshot wound to the head.
Knowledge, if it exists, adds a major dimension to religious commitment.
Kendall Jenner is about to add a major new job to her already extensive CV - the Victoria's Secret show.
Bausch & Lomb would add a major new line of offerings for Valeant, which focuses on neurology, dermatology and generic drugs.
Our conclusions add a major attribute to the previous studies corroborating the Occam razor's principle, especially when simulations are constructed through training and testing phases simultaneously.
The long-standing and well-established public fear of radiation adds a major, perhaps dominating, societal aspect to the scientific challenge.
