In The Global Language Monitor's annual survey of the English language, "Twitter" was said to "stand above all the other words".
Twitter was followed by "Obama", "H1N1", and "stimulus" — referring to the $800bn aid package for the US economy.
"Vampire", the near-ubiquitous suffix "2.0", "deficit", "Hadron" — the object of study of Cern's new atom smasher, "healthcare", and "transparency" rounded out the Top 10.
Paul Payack, president of The Global Language Monitor, said: "In a year dominated by world-shaking political events, a pandemic, the after effects of a financial tsunami and the death of a revered pop icon, the word Twitter stands above all the other words.
"Twitter represents a new form of social interaction, where all communication is reduced to 140 characters. Being limited to strict formats did wonders for the sonnet and haiku. One wonders where this highly impractical word-limit will lead as the future unfolds."
The Global Language Monitor examines the internet, the media and an electronic database to estimate how many times certain topics are brought up.
The Monitor's top words of the decade include "global warming" at number one, followed by "9/11", "Obama" and "bailout".
The top words of 2009:
The top words of the decade from 2000 - 2009:
- Global Warming
- Bailout - The bank bailout
- Derivative - Financial instrument or analytical tool that engendered the meltdown
- Surge - The strategy that effectively ended the Iraq War
- Chinglish - The Chinese-English hybrid language growing larger as Chinese influence expands
- Tsunami - Southeast Asian tsunami took 250,000 lives