The Most Important Words When Learning A New Language

Scott H. Young

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Published in

Mind Cafe

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7 min read

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Apr 8, 2024

When it comes to language learning, grammar gets all the attention. Most theories about second language acquisition focus primarily on how we acquire syntax — the way we put words together to form sentences.

Vocabulary, in contrast, has historically been outside of the spotlight. This is unfortunate. Research has shown that your vocabulary has the greatest effect on comprehension.[1] A major difficulty students have in learning a new language is the sheer volume of new words.

Given its importance, I was pleased to encounter Stuart Webb and Paul Nation’s How Vocabulary is Learned, a research-based handbook for teachers that looks at how to deal with one of the central difficulties in becoming fluent.

How Many Words Do You Need to Know?

The first step in any journey is figuring out how far you are from your destination. How many words do you need to learn to be fluent?

Right away, this question runs into difficulty. How should we count words?

One way would be to count every distinct spelling in a set of texts. Except, this approach drastically overcounts. It would include regional spelling differences (e.g., color in the US, colour in the UK) as well as numerous grammatical inflections that are almost certainly not stored in the brain as separate words (e.g., difficult, difficulty, difficulties, etc.).

Instead, researchers usually prefer to count word families — which include not only distinct words, but also their related inflections, variations in spelling and derivations.

How many word families do you need to know?

Here, we can take advantage of an empirical finding known as Zipf’s law. This law states that if we rank every word in a language in order from most-used (rank = 1) to next-most used (rank = 2) to least-used (rank = n), a word’s frequency of use is proportional to the inverse of its rank.

This means that the frequency of the second most common word would be roughly equal to 1/2 times some constant. In contrast, the frequency of encountering the 10,000th most common word would be roughly equal to 1/10,000 times that same constant. We would…