Can a precise word total ever be known? No, says Professor David Crystal, known chiefly for his research in English language studies and author of around 100 books on the {#blank#}1{#/blank#}. "It's like asking how many stars there are in the sky. It's impossible to answer," he said.

An easier question to answer, he {#blank#}2{#/blank#}, is the size of the average person's vocabulary. He suggests taking a sample of about 20 or 30 pages from a medium-sized dictionary, which {#blank#}3{#/blank#} about 100,000 entries or 1,000 or 1,500 pages.

Tick off the ones you know and count them. Then {#blank#}4{#/blank#} that by the number of pages and you will discover how many words you know. Most people vastly underestimate their {#blank#}5{#/blank#}.

"Most people know half the words—about 50,000—easily. A reasonably educated person about 75,000 and a really cool, smart person well, maybe all of them but that is rather {#blank#}6{#/blank#}. An ordinary person, one who has not been to university say, would know about 35,000 quite easily."

The formula can be used to calculate the number of words a person uses, but a person's active language will always be less than their {#blank#}7{#/blank#}, the difference being about a third.

Prof Crystal says exposure to reading will obviously expand a person's vocabulary but the level of a person's education does not {#blank#}8{#/blank#} decide things. "A person with a poor education perhaps may not be able to read or read much, but they will know words and may have a very {#blank#}9{#/blank#} vocabulary about pop songs or motorbikes. I've met children that you could {#blank#}10{#/blank#} as having a poor education and they knew hundreds of words about skateboards that you won't find in a dictionary."