WASHINGTON (CNN) -- A giddy and relieved Rebecca Sealfon carefully shouted each letter of the word "euonym" to win the 70th National Spelling Bee on Thursday.

The 13-year-old from Brooklyn, New York, said she knew she had won when she was given the word in the 22nd round. "Euonym" is a good name or appropriate name for a person, place or thing.

After the final word, Sealfon, in a burst of nervous energy, jumped up and down with her arms raised. She yelled "yay!" as they announced her name as the winner, and she balanced the trophy on her head for the cameras.

"I was incredibly lucky. I could have gotten out any round," Sealfon said graciously. Earlier, she was so nervous that she had to sit offstage for part of the contest.

"They shouldn't have the bee, even though I won," the 8th-grader said. "Many children are in grief because they lose, and everyone gets nervous."

Sealfon prevailed against 11-year-old Prem Murthy Trivedi, a 7th-grader from Howell, New Jersey.

He put an extra "l" in the word "cortile," meaning courtyard, and smiled to himself with amazement as he pondered the word he clearly was unfamiliar with.

The two finalists battled it out for five rounds as the only remaining contestants from the original field of 245. The day started with 116 finalists in the two-day show of spelling prowess.

Sealfon, as the winner, receives $5,000 cash, a laptop computer, an encyclopedia and other gifts, not to mention a trophy and fame. Her family watched proudly from the audience.

Contestants ages 9 to 15 grappled with the difficult spellings as they stood before a crowd and television cameras in a large hotel ballroom.

Words like "banausic," meaning practical, and "loxocosm," a measuring device, took their toll on the numbers of contenders.

Some coped with the strain by using humor or by asking for the etymology of words -- a permissible request under the strict rules.

Alex Carter, 12, of South Charleston, West Virginia, did both -- asking first for the "etymology, please," then joking, "spelling, please." He got the word, "oneiric," which means relating to dreams, on his own.

Another contestant, Brian Thomas McDermott, 13, of Riverside, New Jersey, could be seen briefly raising his hands in prayer. Others simply asked to be excused to go to the bathroom.