Vocabulary growth

Also called Vocabulary spurt, Word learning, Lexical development, Vocabulary explosion

How word learning speeds up after the first fifty, what feeds it, and why a device with 40 words on it starves it.

What it is

Vocabulary growth is the rate at which a person learns new words. It starts slowly, a handful of words over several months, and then accelerates sharply, usually somewhere around fifty words and around eighteen months to two years. From then on children pick up new words at a pace that continues through primary school, and a reader keeps adding words for life.

It has two sides: words understood and words used. Understanding is always the bigger number.

Who it can help

Anyone teaching, which is every parent, carer and teacher. Vocabulary at five is one of the strongest predictors of reading at eleven, and the gap between children who've heard many words and children who haven't opens early and stays open. Children with developmental language disorder, a learning disability or hearing loss learn words more slowly and need each one more often.

For AAC users, vocabulary growth is only possible if the device grows. A board that stays at forty symbols for three years has decided the person's vocabulary for them. That's a design failure, not a ceiling.

How it works

Children learn words fast because they use shortcuts: they assume a new word refers to a whole object rather than a part, that it's a category rather than one item, and that a word they don't know refers to a thing they don't have a word for. One exposure in a good context can be enough to get a rough meaning, which is then refined over many more (semantics). Adults help most by naming things at the moment of shared attention, by repeating, and by using varied and slightly unusual words rather than only simple ones.

Reading is the accelerator from school age. Books contain far more rare words than conversation does, so a child who reads, or is read to, meets words they'd never hear at home (reading with non-speaking children).

In AAC, a core vocabulary of a few hundred words covers most of what anyone says; fringe vocabulary is the personal and topical rest. Both need to grow, and a good system has a quick way to add a word the day it's needed (personal vocabulary).

Getting started

Pick five new words a week. Real ones, interesting ones, not just labels: "enormous", "squeeze", "furious", "underneath". Use each one a dozen times in real situations. Children learn "enormous" faster than "big" if it's said with feeling.

Read every day, and talk about the words. Stop at one you think is new and say what it means in one sentence. Then use it later, off the page.

If the person uses AAC, add a word to the board every week without fail, and tell them it's there. Model it. A vocabulary that visibly grows tells the person their words are expected to grow with it (teaching a new word).

Where to get help

Speech and Language UK has practical vocabulary resources for families and schools, and a free helpline. RADLD for children with language disorder. In school, the SENCO can arrange a language assessment where vocabulary is a concern.