The rising dollar and sinking oil prices dragged US stocks lower in a volatile week that also included the Apple Watch launch and news of Disney's "Frozen" movie sequel.
The Dow Jones Industrial Average ended at 17,749.31, down 107.47 points (0.60 percent). The blue-chip index had triple-digit swings on four of the week's five sessions.
The broad-based S&P 500 shed 17.86 (0.86 percent) to 2,053.40, while the tech-rich Nasdaq Composite Index lost 55.61 (1.13 percent) at 4,871.76.
"The market is very volatile right now because investors have a lot of questions," said Alan Skrainka, chief investment officer at Cornerstone Wealth Management.
The dollar finished the week at a 12-year peak against the euro after the European Central Bank launched monetary stimulus Monday.
That came on the heels of a strong US jobs report that increased expectations the US Federal Reserve would move more quickly to lift interest rates.
Markets spent much of the week brooding over the speed of the dollar's ascent, as well as the problems associated with a strong greenback, such as the drag on US exports and the hit to emerging economies that hold dollar-denominated debt.
It also hurts the foreign earnings of US companies.
"If you look at the causes for market weakness today, many point to the very significant move higher in the dollar," said David Levy, portfolio manager at Kenjol Capital Management.
"This certainly is viewed negatively by US multinationals earning most of their revenues outside."
- Oil drops again -
The strong greenback also acted as an anchor to oil prices, which are denominated in dollars. US crude prices finished the week at $44.84 a barrel on the New York Mercantile Exchange, down nearly 10 percent from last week.
US oil production remains elevated, prompting a warning by International Energy Agency that US crude inventories are near capacity amid a global crude oversupply.
Lower oil prices offer consumer relief with lower gasoline prices. But they also have bruised petroleum-linked equities and have sparked worries as a sign of economic weakness.
In corporate action, Apple stayed in focus with the launch of the Apple Watch, which can handle messaging, calls and various apps. The device has lifted hopes for yet another winning new product.
But Apple also suffered embarrassment when a nearly 12-hour outage of iTunes and other popular online services depressed sales worldwide.
Disney won cheers from younger fans when it made official its plans for "Frozen 2", a sequel to the 2013 animated movie that earned nearly $1.3 billion and spawned a host of merchandise and theme park initiatives.
General Motors announced $5 billion in share repurchases, averting a proxy fight with activist investor Harry Wilson.
Merger activity remained robust, especially in the highly acquisitive pharmaceutical industry.
Ireland-based Endo International offered $11.25 billion to acquire Salix Pharmaceuticals in a deal that would quash a rival bid from Valeant Pharmaceuticals International.
Mall giant Simon Property also went public with a hostile bid for Macerich, which owns and operates shopping malls in the western US, valued at $22.4 billion.
Next week's calendar includes corporate earnings from FedEx and Tiffany.
But the week's most closely-watched event will be Wednesday's statement by the Fed, which is expected to keep alive the prospects of a rate hike in 2015, perhaps as early as June.
"Whatever the Fed says will be critical," said Tom Cahill, a portfolio strategist at Ventura Wealth Management.