How Many Words Do the Kids REALLY Know?

Memorization, mimicry and matching are not mastery.

The key word in our title is "know."

Knowing a word means to internalize it, not only to memorize, mimic, or match it to its meaning. To internalize a language means to be capable of forming new, original thoughts using the wider vocabulary and not tire easily when reading a greater quantity of words from the wider vocabulary. It can be hard for adults to detect this internalized knowledge level in young children just through observing their speech patterns or their scores from spelling or definition testing.

Repetition Equals Reinforcement

Whenever very young children use a new word, adults are impressed and show it, then repeatedly use it with them. This reinforces the learning and keeps new words from being forgotten.

What if adults could receive this type of reinforcement even if minus the overt praise?


The active vocabularies in the primary language of any typical child under the age of two is usually about 20-40 words. Forming original sentences is still too challenging.


Between the ages of two and three, the child's active vocabulary increases to between two and three hundred, but original "sentences" of more than two to three words are still rare.


It is during the following year when the child begins to use new words and form original sentences daily. At no other time will a child make such steep improvements at a higher speed. It is this child who gives adults most of the impression that children are always better language learners.


The typical four-year-old has a vocabulary of around 1500 words and easily puts together sequential sentences of four to six words including verbs in the simple and continuous tenses expressing the present, past and future. They can suddenly show it bigger and better that they are even smarter than before, and we all marvel at their increased abilities. Most children also begin to mimic adult language phrasing very well at this age, making them appear more mature, and as a result, they appear much smarter too.

However, how much progress can a mature learner make in a new language in four years? Much more than that. Mature ability to learn new words and use ever more complex sentence structures in a new language is superior because mature brains already have a grasp of comparative concepts in at least one other language.

The more one learns, the more one can learn because increasing connections increases the connections that can be made-- exponentially.

How many words do the grown-ups know?

In at least one language, most adults possess a vocabulary of 20,000-35,000 words. With active learning (not just focused language learning), a mature learner's vocabulary has the potential to grow with an average of one entry-- term, sense of term, or other structure--daily until middle age. In fact, the more one does learn, the more one can learn. More current knowledge with which to connect new knowledge increases learning potential.

What about the role of aging in slowing down the learning process?

Slowed learning pace after middle age is not usually due to aging itself but to decreasing exposure to new input which results in fewer new neural pathways. This lack of exposure could be lower exposure to new information (isolation) or the lack of new information available in a particular area (achieved saturation). As we've discussed, lack of new input slows down learning exponentially. Humans can learn new vocabulary and constructs as long as their brains can grow new pathways as there is exposure to new information. It really is as simple as that.

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