Stock Markets Fall Again as Upheaval Continues

By NATHANIEL POPPER and NEIL GOUGH

The global market turmoil intensifies in Asia, Europe and the United States, with the Dow down nearly 700 points in late afternoon trading.

The Upshot

Why the Stock Market Is So Turbulent

By NEIL IRWIN

This turmoil started in China, but it now includes key factors like oil prices, emerging markets and the Federal Reserve.

Migrants Push Toward Hungary as a Border Fence Rises

By ALISON SMALE

On a chaotic path through the Balkans, tens of thousands of migrants are pushing to reach northern Serbia before Hungary seals the border.

Racially Disparate Views of New Orleans’ Recovery After Hurricane Katrina

By CAMPBELL ROBERTSON

A survey found a stark divide among black and white residents over the local economy, the state of schools and the quality of life 10 years after Hurricane Katrina.

Americans and Briton Receive Top French Honor for Stopping Train Gunman

By AURELIEN BREEDEN

President François Hollande awarded the Legion of Honor to four men for their role in subduing a gunman on a high-speed train.

Watch: Train Heroes Honored

Europe Facing New Uncertainty in Terrorism Fight

Israeli Villages Near Gaza Rebound Warily Year After the War

By ISABEL KERSHNER

As new families move in and development plans are made, residents of kibbutzes near the border live with apprehension about the possibility of another conflict.

Walking in War’s Path

HEALTH | Well

Square Root of Kids’ Math Anxiety: Their Parents’ Help

By JAN HOFFMAN

So-called math-anxious parents who provided frequent help on homework actually hurt their children by passing on their anxiety, a study found.

Interactive: Do You Have Math Anxiety?

| The Upshot

No, You Do Not Have to Drink 8 Glasses of Water a Day

By AARON E. CARROLL

There is no science behind a formal, one-size-fits-all requirement of daily water consumption.

Video: ScienceTake | How the Boa Kills

Understanding how a boa constrictor’s grip is deadly.

Video: The Keys to Trump’s Appeal

Donald J. Trump is leading the polls in the Republican presidential race, and he does well with nearly every voter demographic. But pollsters still struggle to to define what drives his supporters.

Video: Bill Cunningham | Jazz Age Lawn Party

Some of the core participants dressed in the authentic flapper style.

Advice After Stock Market Drop: Take Some Deep Breaths, and Don’t Do a Thing

By RON LIEBER

The market is experiencing a plunge, but don’t panic. Here are six pieces of advice to help get you through this unstable period.

News Analysis

Hot Tech Start-Ups May Face a Long and Bumpy Fall

By KATIE BENNER

The worldwide market gyrations will filter down to Silicon Valley, with start-ups that need cash likely to be the first to undergo tougher scrutiny.

Apple Stock Recovers After Tim Cook Email Praises China Sales

By BRIAN X. CHEN

The chief executive of Apple said business was booming in China, where the company has long laid the groundwork to reap big sales.