What is a Multi-Layer Dictionary?

Most dictionaries have two layers:

The long alphabetical list of all headwords and their definitions.
The "defining vocabulary" = the words used to write all the definitions.

To understand a dictionary's definitions, you need to understand the words in the defining vocabulary. Since a typical learner's dictionary has a defining vocabulary containing 2000 or more words, you must already have at least an intermediate-level vocabulary to use the dictionary.

A multi-layer dictionary, like Learn These Words First, is different: The definitions are arranged in layers so they can be understood by learners with different levels of vocabulary:

Basic vocabulary: The most basic words are explained for beginning-level learners, using illustrations, translations, etc. These words are presented in a series of short lessons.
Defining vocabulary: These intermediate-level words are explained using only the words from the basic vocabulary lessons.
Full dictionary: This includes advanced-level words, all explained using only the defining vocabulary.

The problem of circular definitions

Here is an example of a circular definition. The word easy is used to define difficult, and the word difficult is used to define easy:

difficult = Not easy.
easy = Not difficult.

Here is another example. If you do not already know any of these words (illness, sick, sickness), you will not get a helpful explanation of what they mean from these circular definitions:

illness = Sickness of body or mind.
sick = Suffering from an illness.
sickness = The condition of being sick.

Most dictionaries contain thousands of circular definitions like these, especially for the most basic words. This may not be a problem for someone who already has a large vocabulary, but circular definitions are frustrating for beginning-level learners.

The Learn These Words First dictionary is structured in a new way to eliminate circular definitions. The 360 words in the lessons are arranged in an order that allows each new word to be explained using only words that were explained earlier in the lessons. The rest of the words in the dictionary are defined using only the 360 words from the lessons. A computer program was used to check that the lessons and definitions contain no circular definitions.

What is in each layer?

The Learn These Words First dictionary is arranged in layers to eliminate circular definitions and make the dictionary accessible for beginning-level ESL students:

Lessons 1 and 2 use captioned illustrations to explain essential words (NSM universal linguistic concepts). Translations are given in multiple languages.
Lessons 3 through 12 build the vocabulary one word at a time. Each word is explained in English, using only words that have already been introduced. Lessons include example sentences and questions to help review new vocabulary.
The alphabetical index lists the 2000 words in the Longman Defining Vocabulary. Each of these words is defined using only the 360 words from the lessons.
Using the 2000 words from the layers above, students can read any definition in the Longman English Dictionary Online.

Why learn these 360 words first?

Many language courses teach vocabulary in topical lessons of about 30 words each (food, animals, clothing, colors, family, etc.). After learning 360 words in your first 12 lessons, you may understand words for about 12 topics, but the words you know will probably be inadequate for explaining most ideas outside of these limited topics.

Instead of arranging words by topic, the lesson vocabulary of Learn These Words First was carefully selected to maximize the explanatory power of your first 360 words:

The lessons teach most of the highest-frequency words in English. After learning these 360 words, you will know more than half of the words you see on any typical page of English text.
These 360 words are powerful for explaining things: They can explain all the other words in the dictionary. (They are used to define all 2000 words in the Longman Defining Vocabulary, which is used to define every word in the Longman Dictionary.)
By learning these words first, you can use an English-English dictionary, so you can be immersed in English instead of relying on a bilingual dictionary.

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