Gustavo Sabillon, originally from Honduras, reads from his English language textbook at the English Center June 16, 2006 in Miami, Florida. A new study states that the average English-speaking adult knows more than 42,000 words. Joe Raedle/Getty Images

Many English-speaking adults know more than 42,000 words. That is a fact after researchers were able to determine the figure thanks to a study that was spearheaded in the Netherlands.

"Frontiers in Psychology" recently published the study that reveals that a native English speaking American knows that many dictionary words by the age of 20. The study stemmed from an online vocabulary test that was created, originally, to assist with the study. It is the largest study of its kind ever attempted.

The test was developed after a Netherlands television station asked Professor Marc Brysbaert from Ghent University in Belgium to organize a nation-wide study on vocabulary knowledge, according to

“The test we developed was featured on TV and, in the first weekend, over 300 thousand Dutch speakers had done it – it really went viral,” Brysbaert stated.

The test was developed after many were curious to find out how many words a typical native speaker knows.

“The answer starts with a deep sigh, followed by the explanation that the number depends on how a word is defined,” the study — written by Brysbaert as well as Michaël Stevens, Pawet Mandera and Emmanuel Keuleers — explained.

“As a result, in the literature one finds estimates going from less than 10 thousand to over 200 thousand,” the study continues. “In this paper, we try to give practical answers for American English depending on the definition of a word, the language input an individual is exposed to, and the age of the individual.”

After the test went viral, the team developed it in both Spanish and English. The English test has been taken by nearly one million people now.

The test, which takes up to four minutes to complete, is simple: The taker is first asked if the word on the screen is, or is not a word in English. Each one of the tests includes 70 words and 30 letter sequences that look like real words, but do not actually exist.

After linking the test results with users’ age gender, native language and education level (which the taker discloses), the team was able to determine that the average age of a 20-year-old American English speaker knows 42,000 words.

The test also revealed that as one gets older, one new word is learned every two days.

The findings from the study will allow the team to look at how well people know certain words which, in the long run, will be helpful for language education.

Brysbaert sees the study being a key reference point for language researchers in the future as well: “I can imagine future language researchers will be interested in this database to see how English has evolved over 100 years, 1000 years and maybe even longer,” Brysbaert stated.