* Euro falls versus dollar and yen after ECB's Draghi comments
* January retail sales beat expectations, but worries remain
* Greenlight's Einhorn sues Apple, seeks bigger payout
* Indexes: Dow off 0.5 pct, S&P off 0.4 pct, Nasdaq off 0.5 pct
NEW YORK, Feb 7 (Reuters) - U.S. stocks fell on Thursday as comments by the ECB president on the euro raised worries about Europe's outlook and curbed investors' appetite for risky assets.
The euro currency dropped against the safe-haven dollar and yen after European Central Bank President Mario Draghi said the exchange rate was important to growth and price stability, which investors took as a sign the bank is concerned about the euro's advance in recent days.
Materials shares were among the weakest performers on the S&P 500, with the S&P 500 materials index down 0.7 percent, while housing stocks also declined. A housing sector index was off 1.4 percent.
Despite the day's decline and weakness earlier this week, the stock market has been in an almost uninterrupted uptrend for most of the year, with the S&P 500 gaining more than 5 percent for 2013.
Many investors could see buying opportunities in the decline.
"I don't think there's the systemic risk that we had some time ago of bank failures in Europe and so forth. They seem to be ahead of that sort of crisis," said Dan Veru, chief investment officer of Palisade Capital Management, in Fort Lee, New Jersey.
The Dow Jones industrial average was down 67.95 points, or 0.49 percent, at 13,918.57. The Standard & Poor's 500 Index was down 6.31 points, or 0.42 percent, at 1,505.81. The Nasdaq Composite Index was down 16.76 points, or 0.53 percent, at 3,151.72.
Top U.S. retailers reported strong January sales after offering compelling merchandise that drew in shoppers facing a hit to their take-home pay from higher payroll taxes. But an index of retailers was down 0.3 percent.
Macy's Inc rose 1.5 percent to $40.09 after reporting January same store sales rose 11.7 percent.
But Ann Inc dropped 6.7 percent to $30.59 after forecasting fourth-quarter sales below analysts' expectations.
Fund manager David Einhorn's Greenlight Capital on Thursday said it has sued Apple Inc and said the company needs to do more to unlock value for shareholders. Apple shares gained 0.6 percent to $457.43.
Akamai Technologies Inc lost 15.6 percent to $35.06 as the worst performer on the S&P 500 after the Internet content delivery company forecast current-quarter revenue below analysts' expectations.