By the time Odily Sanchez Segura saw her bike for the first time, it had crossed a sea, sped through cities and mountains, and jolted over rough dirt roads deep into a reserve for an isolated tribe of native Costa Ricans. It had floated 40 minutes in a canoe along a river lined with plantain trees, and then, with several other bikes donated in suburban Washington, bounced miles over a jungle path to Coroma, a small village of thatch-roofed huts on stilts.

Odily, who’s 10 years old and skinny, looked at it: bright green, fat tires, a tough little mountain bike. She didn’t smile — not yet. It was too important.

She and her 13-year-old brother would use the bike to get to school. They were two of the lucky ones in a place where people are without electricity, running water and, for the most part, any belongings at all, where many children can’t get an education because they live too far from the nearest school.

Odily’s 15-year-old brother had to walk two hours each way to get to class. But this was progress: Odily’s grandparents didn’t have schools. Her parents finished primary school. Her mother, Gloria Segura Martinez, hopes her children will go to college.

The bikes, she believes, will help take them there.

Odily stepped toward the iridescent bike. She looked back at her mother, dark eyes all question.

Segura smiled at her. “Go ahead,” she said. “It’s yours!”

* * *

Three months earlier, Peter Rushford had pulled into a parking lot at Baileys Crossroads on a chilly March afternoon, swung open the back of his SUV and started unloading bikes that his family no longer wanted. There were six of them, including the bright green mountain bike that his 20-year-old daughter, Carly, had once ridden to swim-team practice.

The bikes had been lying under the back porch of the Rushfords’ cedar-shingle-and-stone home in Potomac near Congressional Country Club. Then one of his son’s friends said he was doing a collection for a group called Bikes for the World.

The Arlington County nonprofit group takes thousands of unwanted bikes in suburban Washington — where things go from coveted to clutter in an instant — and sends them overseas to people who need them.

Its founder, Keith Oberg, knows how much of a difference even one bike could make. In the developing world, bikes can transform lives — increasing the number of people a public-health nurse can treat, helping a farmer deliver his fruit to a better market or making it easier for a family to get clean drinking water.

Each bike he sends to Latin America or Africa has a story. There’s a red Trek that a Frederick woman took on a grueling AIDS fundraising ride after a friend died of the disease. There’s a Viscount, custom-built in London for a Potomac woman’s cycling trip across Europe. There’s a little Murray with training wheels that an Arlington boy spotted behind the Christmas tree a few years ago and begged his parents to let him ride in the snow.

The bikes donated by the Rushfords included two that Peter and his wife, Susan, had ridden as newlyweds along the C&O Canal.

“I’m just happy they’re going somewhere they can be used and appreciated again,” said Peter, 54. “Have a second life.”

The Rushford bikes were eventually wedged with hundreds of others into a 40-foot-long shipping container. Oberg, 60, climbed onto the tower of sardined bikes to squeeze a box of extra pedals into a crevice and ease more children’s bikes in, wiggle by wiggle.

As he worked, one of his two employees drove up with 28 bikes he had just scavenged from the dump. Some looked brand new.

“Montgomery County’s affluence,” Oberg said. “It’s amazing what people throw away.”

Finally, the container was full to bursting: 507 bikes.

“That fits nicely!” Oberg said, and when the volunteers laughed, he said, “Well, it fits.”

* * *

The sun had just come up in Costa Rica’s capital when Steven Fonseca Ortiz drove a diesel pickup loaded with the green mountain bike and five others from Washington through the crowded streets of San Jose, toward the mountains beyond still wrapped in mist.

Fonseca, 21, works for the Fundacion Integral Campesina, a nonprofit group that works with Bikes for the World in Costa Rica. FINCA encourages people in rural areas to form collective banks with tiny amounts of capital, lending money so that someone can start a business.

Fonseca was delivering these bikes 150 miles to Talamanca,home to the Bribri and other indigenous people. Remote and sparsely populated, it is the poorest canton in Costa Rica. The average person has finished fourth grade.

To get there, the truck sped through vast fields of bananas and plantains, then bounced over big rocks through thick forest. Finally, in a small town along the Telire River, two Bribri men helped Fonseca haul the bikes into their narrow boat.

Lisandro Diaz, 59, carried a silver bike that had belonged to the Rushfords. He smiled broadly: This one would be his.

His 23-year-old son, Juan Miguel Diaz, had picked a red mountain bike, donated by an Arlington lawyer. “Once you get to where I live, you will see why I need the bicycle,” he said and smiled, just like his father.

On the river, the Talamanca mountains loomed high and dark. Occasionally a snowy egret would lift off among the reeds, but there were no other signs of life. Forty minutes later, the boat bumped up at a small clearing, and they lifted the bikes out.

Lisandro Diaz and the others began pedaling the bikes down a long, muddy path to Coroma, a lush village of a few hundred Bribris who eke out a living harvesting bananas and plantains.

Coroma had seen bikes before. But the arrival of six at once was startling. Two little girls hid behind a palm, staring at the bikes. Three boys raced up to them, touched one and dashed away.

Odily’s mom, who runs a newly established FINCA collective here, handed out loan applications for others to fill out. The bikes were being sold for $20 to $40, with loans of about 1.5 percent interest.

Diaz ran his hand over the silver bike he was buying. It would help him travel long distances between plantain and banana farms and to reach the river to run his boat service.

“These are my favorite colors, silver and blue,” he said, touching a fender and beaming.

The Bribri were all looking at the bikes, teasing one another, trying to lower the seats. Diaz rang the bell on one, startling them; they all burst out laughing.

Odily swung a skinny leg over the green bike, pushed the pedals unsteadily and wobbled down the path.

* * *

The next evening, Odily’s mother and father sat on the floor of their tiny home, bouncing their baby in the flickering light of two candles and talking with Fonseca about the way their lives had changed and what the future might hold.

Odily hopped onto an unsold bike and rode it slowly, one foot on the floor, one hand brushing the wall, listening to the adults talk.

When her grandparents were children, they knew only the native culture and spoke only Bribri. When an outsider came to the community, they would hide, unable to talk, said Odily’s father, Freddy Sanchez Verche. “They were isolated.”

Odily’s parents learned Spanish in school. “So now we’re connected to the world,” Sanchez said.

A doctor comes a few times a month. There are schools, including one opening in Coroma. And the government is building houses for some people; theirs is almost finished, with cornflower-blue paint on the walls, a sink and shower outside. It even has switches for electricity.

“They say it is coming,” said Odily’s mother, although they don’t know when or how.

Sanchez has seen a lot of friends leave. “To get money,” he said. “To get a better job.” They come back unhappy, he said, with more things and more problems.

Still, they want their children to leave Coroma to go to college. “I don’t want them working like I do, in the hot sun, working hard with plantains,” Segura said.

Alonso, 15, wants to be a surgeon.

Joel, 13, said he wants to learn English and teach in Coroma. “Because we don’t have anyone to teach us English here,” he explained.

When Joel turned 12, six of the 10 students in his class stopped going to school because they had to work or because it was too far. Even the teachers have trouble getting there, crossing rivers and trekking miles through the jungle in black rubber boots.

Many more children could go to school if they had bikes, said Odily, whose primary school is not nearly as far from their home as the secondary school where Alonso now studies.

“I want to be a Spanish teacher here,” she said, “because there are children who can’t study here. I want to help them.”

The next morning at dawn, with roosters crowing wildly in a dense fog and the family’s pig, Pancha, wandering around snorting, Alonso left for class on his new bike. It would take him an hour with the bike.

Odily came back from her bath in the river, put on her navy-and-white uniform, then hopped on her green bike. She looked back shyly and smiled, then bounced down the path past the cacao trees, heading to school.