Structure and wording for readability

Whether individual words are readable and understandable depends on a combination of their length and familiarity, which will vary with the reader. Those with limited vocabularies, such as people with low reading skills or users of English as a second language, are likely to be less familiar with many words.

Word length

One of the most obvious features of words is whether they are short or long. Although ‘short’ and ‘long’ are relative terms, the average length of words in the text can provide a measure of whether it is likely to be more or less readable for many readers. The average word length of your text is calculated by counting the total number of characters in every word and dividing it by the total number of words.

But average word length is only a rough measure of how difficult or easy the text will be for the average reader. This is because longer words are not always harder to understand:

And shorter words are not always easier to understand:

Word difficulty

The perceived ‘difficulty’ of a word is often about how familiar it is to the reader.

It is hard to say exactly which words are likely to be familiar to adult readers, because of individual differences in language skills, reading ability, education, professional training and employment.

But a general measure of the familiarity of words is their frequency in common reading material, such as newspapers. Lists of more common words and their frequencies are available from international reference databases such as CELEX(Opens in a new tab/window), or dictionaries for learners of English as a second language, such as the Longman dictionary of contemporary English. Dictionaries for learners of English as a second language try to define only the 3,000 most commonly used words, so that they are as useful as possible for those with limited vocabularies.

You can check the vocabulary range of your text against such resources.

Technical words

Some texts will need to include technical terms. Readability will then depend on how familiar a reader is with the terms and the subject area.

Sometimes you will need to convey technical ideas to both specialist and general audiences. For example, communicating health advice or computer instructions to the general public may involve using technical language.

To make sure general readers can understand text that includes technical terms:

• limit the number of technical terms by paraphrasing or using alternatives

• explain any potentially unfamiliar or technical terms by providing clear definitions, or highlighting key words and their definitions in boxes.

Sentences that are long or complex are difficult for readers to process, especially if the grammar and structure are unfamiliar.

Sentence length

The average sentence length of your text is found by counting the number of words in sentences and dividing by the number of sentences. But, just as for average word length, this is only a rough measure of how difficult or easy the text will be to read.

The ideal average sentence length depends on the audience. In general, the broader the audience, the shorter the sentences should be: an average of 15 words per sentence for text for a general audience and no more than 25 words per sentence for more technical text. Your content is more likely to be understood by those with limited English if it is expressed in shorter sentences.

This does not mean that shorter is always better. Even very short sentences can be less readable if they chop the material up too much. A paragraph of 4 very short sentences may actually be less readable and convey less meaning than a paragraph of 2 longer sentences:

A mix of shorter and longer sentences that are connected is the best way to keep readers engaged. Too many short sentences can lose meaning; too many long ones lose the connections between sentences in a haze of words. See Clear writing for further discussion of sentence lengths for different publications.

Sentence order and complexity

Readers naturally find it easier to process sentences that present the subject matter in a meaningful order. For example, you would probably find the first example below easier to read than the second:

Although the second sentence is shorter than the first, it may be more difficult for readers because its main idea (longer sentences are difficult to understand) is broken up by other words that are not as important. Readers have to detour through the less important words before coming back to the main statement to finish the sentence. In the longer version, the main idea is delivered in full at the start of the sentence, and other information is added after it.

Complex sentence construction can cause particular difficulty for readers of English as a second language, especially if the grammar and sentence order in the user’s first language are different from English.

For example, in English sentences, different sentence openings can be used to vary the focus, but their variability is a known challenge for second-language users:

The first 2 sentences in this example start with the same structure – the subject and an active verb. But the third sentence starts with a conditional clause, and is also more passive. This variation is fine for first-language users of English, and probably helps to refresh their attention. But for second-language users, it may make it difficult to understand the continuity between the 3 sentences.

Text formats

The structure and formatting of text on a page can affect readability. Most readers find formats that have shorter paragraphs and generous use of white space easier to read, and pages of long, densely spaced paragraphs harder to read.

However, the impact of formatting varies with the audience. Those most used to reading newspapers and magazines, which have 1- or 2-sentence paragraphs in columns, will probably find the dense paragraphs of academic and scientific texts unreadable. But researchers may have little difficulty reading such formats.

Explore Structure options to find ways to best structure your text to aid readability.

One way to avoid overwhelming general readers of online information is to introduce a topic with very short sentences. Readers can engage easily with topics presented in a summary format with short sentences and paragraphs, which lead on to fuller information: