Olympic athletes, high-level officials and other people have been arriving in Rio de Janeiro for the opening of the 2016 summer games.
The opening ceremony is Friday night, local time, but some events already started. The first medals will be awarded on Saturday.
The Rio Olympics officially begin Friday, when the Olympic torch is carried into Maracana Stadium to light the Olympic cauldron. The cauldron will stay lit for over two weeks until the closing ceremony on August 21. During that period, 301 gold medals will be awarded to the winners.
At the last summer Olympics, the 2012 London games, the United States won 46 gold medals and 104 medals in all. China was second, with 38 gold medals and a total of 88. Britain finished in third place, with Russia in fourth.
One major question this year is: How many medals will Russia win at the Rio games?
Just before the Olympics started, the International Olympic Committee (IOC) considered banning every member of Russia's team because of a doping scandal.
Investigators for the World Anti-Doping Agency (WADA) found evidence of Russian athletes using unapproved substances at the 2014 Winter Olympics in Sochi. And the agency accused the Russian government of being involved and covering up the activity.
But in the end, the IOC decided not to ban all 387 Russian qualifiers for the Rio games. Many Russian athletes will have a chance to compete. But most of the country's track and field athletes were banned by the International Association of Athletics Federation.
At a meeting in Rio this week, WADA and the IOC criticized each other. WADA officials said the IOC should have banned all the Russian Olympians. The IOC said WADA should have acted faster on the allegations of Russian cheating.
More than 10,000 men and women from over 200 nations will compete at Rio de Janeiro. The first medals, in men's cycling and women's shooting, will be awarded on Saturday. Chris Froome, who won the Tour de France last month, will be representing Britain.
American swimmer Michael Phelps has won the most Olympic medals ever. He has 22 medals, including 18 golds. He will carry the flag of the United States at the opening ceremony on Friday.
Aside from the question of which country will win the most medals, some people are worried about the health of the competitors.
Athletes are being careful about the time they spend out of doors because of concerns about the Zika virus. Zika spreads when mosquitos bite human skin. The virus is linked to microcephaly, a birth defect in which a baby's head is smaller than the heads of other children of the same age and sex.
Olympic organizers say they are not overly concerned about Zika since the games take place during Rio de Janeiro's winter.
Athletes competing in water events, like open-water swimming, rowing and sailing are concerned about polluted water. The Associated Press reports that those athletes run a high risk of getting sick.
Water at some of the competition areas is polluted by untreated waste water. It contains bacteria and viruses carried by human waste.
While some athletes will wear gloves or other protection, it will be hard for the open-water swimmers to keep water from getting into their mouths. Yet Olympic organizers say athletes will not get sick.
April Ross is an American beach volleyball player. She is excited about the chance to compete on the famous Copacabana beach. “I think it's awesome to be playing on an actual beach,” Ross said. But medical experts have warned that even the sand from coastal areas carries viruses.
Ross is one of 292 women on the U.S. Olympic team. The number of women on Team USA (292) is greater than the number of men (263).
Some of the strongest and most successful Americans at the games may be women. Swimmer Katie Ledecky is a world record holder in two Olympic events and won the 800-meter freestyle event in London.
The USA women's soccer team has won three gold medals in the past three summer Olympics. The women's basketball team is trying for its sixth straight gold medal.
Women will also be part of the first-ever refugee Olympic team.
Ten athletes from countries like South Sudan, Syria, Democratic Republic of Congo and Ethiopia will compete under the Olympic flag.
Four of them are women, including Yusra Mardini, a Syrian refugee now living in Germany. She and her sister swam across the Aegean Sea when the motor on their boat failed late last year. She and the other refugees were rescued and taken to a Greek island. Mardini and her sister settled in Germany last year.
Dan Friedell wrote this story for Learning English. George Grow was the editor.
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Words in This Story
dignitary - n. a person who has a high rank or an important position
medal - n. a piece of metal often in the form of a coin with designs and words in honor of a special event, a person, or an achievement
cauldron - n. a large pot
doping - n. the illegal use of a drug (such as a steroid) to improve an athlete's performance
qualify - v. to have the skills that are required or do the things that are required to become a member of a team or to be allowed in a competition
allegation - n. a statement saying that someone has done something wrong or illegal
defect - n. a problem or fault that makes someone or something not perfect: such as a : a physical problem that causes something to be less valuable, effective, healthy, etc.
athlete - n. a person who is trained in or good at sports, games, or exercises that require physical skill and strength
torch - n. a long stick with material at one end that burns brightly
