The phrase "a principal purpose" is correct and usable in written English.
It can be used when discussing the main or primary reason for something.
Example: "The study was conducted with a principal purpose of understanding the effects of climate change on local ecosystems."
Alternatives: "a primary objective" or "a main aim".
Lewis told me that the Gosaibis had decided to quit their pursuit of Stewart in order to focus on reclaiming billions from Sanea, and said, "A principal purpose of the lawsuit against Stewart was to obtain information against Maan al-Sanea".
It said said that in May or June last year, he agreed to travel to a Qaeda training camp "knowing that America and its citizens were the enemies of bin Laden and Al Qaeda and that a principal purpose of Al Qaeda was to fight and kill Americans".
The government's indictment describes Al Farooq as an "Al Qaeda facility," and charges that Lindh went there "knowing that America and its citizens were the enemies of Bin Laden and Al Qaeda and that a principal purpose of Al Qaeda was to fight and kill Americans".
Of course few people would admit they had a principal purpose of tax evasion, and the government had a hard time proving it.
And, in the Goldman Sachs case, a principal purpose of the CDO appears to have simply been to create a vehicle for speculation structured, in large part, to provide Paulson with a means to short the subprime mortgage market.
And this would be fine if, in fact, the churches were living out their claim to fulfill a principal purpose of serving the poor.
Arthur Z. Schwartz, general counsel for Acorn, accused Mr. O'Keefe of "trying to destroy an organization whose principal purpose is to help poor people".
In his 2003 book, "Universities in the Marketplace," Derek Bok, the former Harvard president, made the shocking observation that "faculties currently display scant interest in preparing undergraduates to be democratic citizens, a task once regarded as the principal purpose of a liberal education and one urgently needed at this moment in the United States".
In Inverting the Pyramid, Jonathan Wilson argues convincingly that, in the modern game, scoring goals need not be a centre-forward's principal purpose.
Corner furniture, movable articles, principally cupboards, cabinets, shelves, and chairs, designed to fit into the corner of a room, for the principal purpose of saving space.
Attended by representatives of 35 governments—including the NATO countries, the Warsaw Pact nations, and 13 neutral and nonaligned European states the conference had as its principal purpose a mutually satisfactory definition of peace and stability between East and West, previously made impossible by the Cold War.
