No one knows all the words in English. No one. Several months ago, I wrote about the average size of the native English speaker’s vocabulary (approx. 25,000 words or 15% of all the words in English). Fortunately, the other 85% of words aren’t used that often, but we do encounter them from time to time. 

We come across unfamiliar words while reading or watching a movie. But do we need to understand them to comprehend the message being communicated? If we don’t need to know every single word, how many can we gloss over? What’s the threshold? When does a reading text become too difficult to comprehend? When does comprehension break down in a conversation?

An image of a Charlie Brown doll.

This post is based on a lecture I attended by Dr. Charles Browne (you can guess why he goes by Charles 😉 ) back in 2010. Dr. Browne is an Applied Linguistics and TESOL professor at Meiji Gakuin University in Japan. One section of his lecture really struck me, and it’s something I often shared with my students.

You don’t understand as much as you think you do

I know, you’re smart. You’re well-read, and you have a larger than average vocabulary. You don’t struggle to understand anything. Stick with me, and we’ll put that to the test.

I’ve touched on this idea before. When reading or watching a movie or TV show, you likely don’t understand every single word. This applies to native English speakers and non-native English speakers alike.

You may think you understand every word, but some examples later will prove that you don’t. And if you do, then you’re free to tell me all about it in the comments.

Why does it matter if we don’t understand every word we hear or read? What percent of words do we need to understand before comprehension becomes difficult, if not impossible? 

A close up image of a street with the words What do you mean written in chalk.

When giving this lesson to my students, I’d ask them what they thought the average English speaker’s vocabulary size was. I’d also ask them how many words a person needs to understand everyday conversations. BTW, the answers to these questions are in the blog post I linked to above.

I would then ask them the following question:

On one page of text, what percentage of words do you think you need to know to understand what you’re reading?

  • 70%
  • 75%
  • 80%
  • 85%
  • 90%
  • 95% 
  • 100%

What about you? What do you think? Go ahead, pick a number. I’ll wait.

Let’s read a little story about a student named Carla

Now I’m going to show you a short passage. There are a total of 89 words in this paragraph. Did you guess that you could still comprehend a text, understanding only 75% of the words? BTW, that’s 22 /89 words, here’s what that would look like.

A screenshot of a paragraph with 22 out of 89 words missing.

I’ve chosen to remove the words to make my point. If you don’t understand a word, it’s essentially the same as the word not being there. So, do you understand what’s happening in this passage?

You can discern that it’s about a student named Carla that plays some sport. If I asked you to explain this to someone else in your own words, could you? Without adding any of your guesses about the missing words? 

No. Comprehension is impossible with 25% of the words missing (or not understood). You can have an idea of what the passage is about, but only in the most general sense. It would be insincere to claim you understood the passage.

What happens when we increase the number of known words from 75% to 85%? Understanding 85% of the words, the passage must be comprehensible. That’s only 13 words from this passage that you can’t understand.

A screenshot of paragraph with 13 out of 89 words missing.

We now understand a little more. We perhaps even feel pretty confident that we have the whole picture and can fill in the blanks. But how did Carla feel during warm-ups? Who was watching? How did she feel when the tryout results were posted? We can guess, and our guesses may be correct—but we can’t be sure. 

We have a much better understanding. But there are still too many unknowns to claim we comprehend this passage. If one of our guesses is wrong, it could change the narrative quite a bit. Were her parents watching? Were some hot guys from the boy’s team watching? Were university scouts watching?

Even understanding 85% of the vocabulary isn’t enough. How high do we have to go?

If we decrease the number of missing words from 15% to only 5%, that means only four words are missing. What does that look like?

A screenshot of paragraph with none of the of 89 words missing.

With only four words missing, or 95% understanding, we can now say we understand this text. We could explain it to someone without having to guess about missing information. It turns out, 95% is the ‘magic number’ for facilitating comprehension with reading or listening. 

It’s the threshold learners can read without consulting a dictionary. If we don’t understand more than 5% of the words being used, we struggle with comprehension.

Dr. Browne cited two studies in that lecture I attended over a decade ago. The first claims that comprehension is almost impossible when we comprehend less than 80% of the vocabulary (Hu & Nation, 2001).

The number of 95% is the point at which learners can read without the help of a dictionary (Laufer, 1989). How often do you look up words in the dictionary when you’re reading?

Dictionaries are more accessible than ever, but…

These days, it’s easier than ever when reading on your Kindle. You simply click a word to get a definition. But how often do you do that? When it dramatically impacts your ability to understand a passage or a concept, you may look it up. But if you understand more than 95% of the words on the page, you likely skim right over that unknown word. 

Here’s the passage in its entirety, in case you were curious.

All this may be true for learning a foreign language, but not my native language!

Are you sure? Have you ever struggled to comprehend a passage, particularly a difficult academic text? Remember how much fun university was? 

I’m sure you’ve seen movies like The Matrix and TV shows like C.S.I., Law & Order, and E.R.(kinda showing my age, huh?). I know you understood The Matrix. And you either loved it or hated it. But did you understand every concept? I mean, really understand it? After how many viewings? 😉

You’re bright. You read tons more than all your friends. Your vocabulary is more extensive than most. I’m sure you’ll have no trouble with this passage:

A variegated complex of elements considered as it is before being organized. For Kant especially, the sensory manifold in the as yet unstructured variety of material presented to the senses, which the mind then organizes through concepts, so that perception results.

(A Dictionary of Philosophy, A.R. Lacey, 1976)

No problem, right? I straight up admit I had to look up ‘variegated’ (distinguished or characterized by variety). Complex doesn’t mean difficult to understand—though it should! In this passage, it’s a noun, not an adjective. BTW, this is a definition for the term ‘manifold’—from a dictionary of philosophical concepts.

A picture of a small metal statue of The Thinker against a white background.

I estimate that the average person might struggle with three words here: variegated, complex, and manifold. You’re probably familiar with (or have at least heard of) complex and manifold, but not how they’re used here. If so, you don’t understand 7% of the words in this passage.

Maybe you’re beginning to understand how comprehension can suffer—even when you understand 90% of the words. After reading this definition from the FreeDictionary, this concept started to make a little more sense: 

7. (Philosophy) (in the philosophy of Kant) the totality of the separate elements of sensation which are then organized by the active mind and conceptualized as a perception of an external object


A bit abstract, but I think I get it now. But it was no easy task, and struggling to understand all the words in the initial definition made the task that much more challenging. I certainly didn’t understand it after my initial reading or without looking up words in the dictionary.

Perhaps you’re a philosopher, and that passage posed no challenge

Let’s take this passage from a popular TV show, House (

House: Are you in first year of medical school? No. First of all, there’s nothing on the CAT scan. Second of all, if this is a horse then the kindly family doctor in Trenton makes the obvious diagnosis and it never gets near this office. Differential diagnosis, people: if it’s not a tumor what are the suspects? Why couldn’t she talk? 

Chase: Aneurysm, stroke, or some other ischemic syndrome. 

House: Get her a contrast MRI. 

Cameron: Creutzfeld-Jakob disease. 

Chase: Mad cow? 

House: Mad zebra. 

Foreman: Wernickie’s (sic.) encephalopathy? 

House: No, blood thiamine level was normal. 

Foreman: Lab in Trenton could have screwed up the blood test. I assume it’s a corollary if people lie, that people screw up.

A picture of street graffiti of the TV character House, with the words "You are going to die" above the face and the words "It's not lupus" below the face.

What’s a differential diagnosis? If you watched enough episodes of House, you might have figured that one out. Do you know the difference between an aneurysm and a stroke? What’s an ischemic syndrome? What are the symptoms and side effects of Creutzfeld-Jakob disease?

What’s Wernicke’s encephalopathy (misspelled in the transcript)? For that matter, what’s encephalopathy? FYI, tells me it’s “…any degenerative disease of the brain, often associated with toxic conditions.” Oh, and what’s thiamine?

This comes from what I assume is a 15–30 second scene. There are 108 words, not counting the character names. Without any medical background, it’s unlikely the average person understood that passage in its entirety. But we got the gist. 

Someone is unable to speak. The doctors don’t know why. They suggest several rare diseases, but none of the tests supports that hypothesis. But can you say you ‘understood’ that passage?

I would suggest that the above passage is bordering on an inability to comprehend. Other than getting the gist of what’s happening, most viewers wouldn’t understand exactly what the characters were talking about. And in TV shows, movies, and books, that’s often okay. 

A picture of an x-ray of hand making the universal sign for OK.

We don’t need to understand every word. But we also don’t take the time to stop and look each one up. We gloss over them, fill in the gaps as best we can, and are satisfied with that. But if that conversation had gotten much more ‘technical’, the audience may have been completely lost.

What does all this mean?

It depends. If you’re studying English as a second or foreign language, choose simple reading materials. If you struggle to understand much more than 5% of the words on the page, you may get frustrated and give up. You’re studying a new language—it’s already challenging enough. Don’t make it even harder on yourself.

The same goes for choosing TV shows or movies to watch for language study. You can refer to my previous post about how to choose suitable TV shows for learning a language

If you’re an ESL/EFL teacher, keep this in mind when choosing content for your students. Particularly when selecting reading and listening resources. Reading can be great a way to learn new vocabulary. But if there are too many new words, your students may struggle to comprehend the material.

There’s a takeaway for those of you who sometimes watch translated TV shows or movies. Remember that the translator that wrote the subtitles for that medical drama likely doesn’t have a medical degree. But they had to reach enough of an understanding to write ‘something’ in the target language. 

An overhead shot of woman sitting cross-legged on a bed with a laptop, several books and a day planner surrounding her.

That likely required research to understand the passage in the source language. Then they had to find the correct word or phrase in the target language. Don’t forget; they could easily be translating a courtroom drama next month. And a documentary on a football hero the month after that.

The next time you watch a movie or TV show, keep an ear out for words, phrases, and jargon that you don’t actually understand. You may be surprised how many instances you find! 

No trouble understanding everything in this post? Let me know in the comments! Did I make you think about comprehension and understanding in a different light? I’d love to hear about that too!

3 thoughts on “How many words can you gloss over and still understand something? 

  1. What an interesting post. And yeah, I’m learning a new language (Chinese), and am starting with the most basic stories (HSK Level 3) because anything beyond that just frustrates me. Thanks for this post!

    1. Thanks! Glad you found it interesting! Best of luck with Chinese…I struggle enough with Korean!

      Choosing material you can digest will certainly make your learning experience more enjoyable.

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