Cognition
What Does It Mean to Know a Language?
Having a large vocabulary and verbal fluency are desirable, but not essential.
Posted May 5, 2025 Reviewed by Davia Sills
Key points
- "Knowing" a language can mean different things to different people.
- Depending on a learner's goals, some aspects will be more important than others.
During a conversation with a colleague the other day, my coworker made an observation that surprised me.
He is a professor of French and has taught that language at all levels for over three decades. And yet, he admitted that there are several hundred or even thousands of words that he knows in English—his first language—for which he doesn’t know the French equivalent.
Specifically, he alluded to the names of animals and plants that he has simply never encountered in his second language. Does this mean that, at some level, my colleague doesn’t know French? And this caused me to wonder: What does it mean to know a language, anyway?
Learning Versus Memorizing
If we use a person’s vocabulary as a yardstick for measuring linguistic proficiency, we quickly run into problems.
Consider the case of Nigel Richards, who won a Spanish Scrabble tournament in 2024. Richards is an English-speaking New Zealander who cannot hold a basic conversation in Spanish. Instead of learning the language, he used his eidetic imagery ability to memorize all the words on the Spanish Scrabble word list. (Richards employed the same strategy to also win two French-language world championships.)
Furthermore, Richards isn’t unique—many of the world’s best English Scrabble players hail from Thailand, and some of these champions can’t speak English at all.
For that matter, how well do native speakers of English measure up? It’s been estimated that adults typically know the meanings of between 20,000 and 40,000 words. That’s an impressive number, but it’s only a small fraction of the 600,000 word forms that appear in the Oxford English Dictionary. In other words, adult speakers of English may only know about 5 percent of the words in their native tongue.
How Low Can You Go?
At the other extreme, what about individuals who learn only a narrow subset of terms for a specific purpose?
Airline pilots who fly internationally, for example, are required to obtain a passing grade on the Test of English for Aviation (TEA). This exam assesses comprehension and production of English, but it is limited to Aviation English, an international standard that consists of about 300 words. This allows them to communicate effectively with air traffic controllers and other pilots. But does this mean that these pilots know English?
How about the individual who masters a rudimentary set of conversational expressions in a phrasebook before making a trip to another country? They might be able to function reasonably well in a foreign land as long as the interactions they engage in are fairly routinized, such as ordering food or buying souvenirs. But does this mean that the tourist, with a minimal vocabulary, “knows” the language?
Some individuals who experience brain injury are diagnosed as having expressive aphasia. They can still comprehend spoken language, but they may exhibit great difficulty in generating fluent, grammatical speech. When this happens, we don’t say that the individual has lost their linguistic knowledge. It’s assumed that they still “know” their native language, but that their injury has disrupted their ability to produce it.
Who “Knows” a Language?
If we stipulate that knowing a language means knowing the meanings of many words, we can group together the French professor, native speakers, and aphasics, who possess this knowledge, and that this differentiates them from the Scrabble champions, pilots, and tourists, who do not.
On the other hand, if our criterion is conversational fluency, the French professor and native speakers still clearly qualify. Scrabble champions and aphasics, however, do not. And the pilots and tourists become problematic cases—they can converse with others, but only in a limited way and in specific contexts.
And we’re not out of the woods yet. Students in some degree programs are required to demonstrate a “reading knowledge” in one or more languages. This means they can make sense of written texts and documents within their specialized discipline. A graduate student of continental philosophy, for example, might need to demonstrate a reading knowledge of German. But they may have little or no ability to speak or to write in that language. Does this mean that the student doesn’t “know” German?
In contrast, children acquire the ability to speak proficiently before they learn to read and write, and some adults never acquire these skills. But it would be strange for someone to claim that an illiterate adult doesn’t know their native language.
Cultural factors must be considered as well. Another colleague of mine works for the U.S. government. He has passed proficiency exams in Japanese and is conversationally fluent in that language. Nevertheless, he confessed to me that he sometimes struggles to make sense of stories in Japanese newspapers because they assume a level of cultural knowledge that he doesn’t possess. Does this mean that he doesn’t “know” Japanese?
These examples illustrate the dangers of defining the knowledge of a language in terms of vocabulary size, speaking ability, or even the ability to read and write. Language is multi-dimensional, and one can be said to know a language in a variety of ways and use it for a variety of purposes.
