Should you define an abbreviation more than once with the tag?

Question

If I have an article or blog post and I have an abbreviation or acronym such as SAD (Seasonal Affective Disorder) should I do this everytime the acronym SAD appears in a document?

<abbr title="Seasonal Affective Disorder">SAD</abbr>

If you do only define it once, does it have to be the very first time the abbreviation appears or could it be the 3rd or 4th time?

score 6 · Accepted Answer · answered Sep 12 '11 at 11:48

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As per Wikipedias Manual of Style you should only explain an abbreviation once. I would extend this to your case as well and only use the abbreviation on first occurence.

answered Sep 12 '11 at 11:48

Pål Brattberg

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score 6 · Answer 2 · answered Sep 12 '11 at 12:13

This depends on how you document is structured and how you expect people to arrive at and read the document.

For instance, if there are multiple anchors in the document and the user could arrive at the middle of the page from another page or jump down the page from the top of the page, then it would be best to use <abbr> in every instance... to ensure the visitor gets the explanation.

Moreover, for accessibility, it would be best for those who use screen readers to hear the abbreviation read out.

Good point that users don't actually read from top to bottom. — Pacerier, Jul 13 '12 at 00:09

Mo Beigi · Answer 3 · 2011-09-12T11:57:26.840

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Preferably you should define an acronym whenever you use it, however defining it once in a document is also acceptable.

Alternatively to make constant defining easier you could assign the above string to a php variable and use that to output the the html if it was a really that commonly used.

Edit: From a SEO point of view you would want to preferable change the first occurrence as the first occurrence is what many search engines use to assign certain characteristics in a page.

edited Sep 12 '11 at 11:57

answered Sep 12 '11 at 11:52

Mo Beigi

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Although these were all good answers, your point about SEO was a good one. – punkrockbuddyholly Sep 12 '11 at 17:44

score 2 · Answer 4 · answered Sep 14 '11 at 14:10

The first occurence should be explicited.
Criterion 9.3 from Accessiweb reference list summarizes it well (test #2 for abbreviations)

On each Web page, does the first occurence of each abbreviation pass one of the conditions below?
- The abbreviation is provided with its meaning as an adjacent link
- The abbreviation is implemented via a link referring to a page or a location on the page allowing to know its meaning
- The abbreviation is included in a link with a title attribute allowing to know its meaning
- The meaning of the abbreviation is available in a glossary on the site
- The abbreviation is implemented via an abbr tag with a title allowing to know its meaning

Relevant WCAG 2.0 sufficient techniques are (not normative, you may come with your own implementation):

Should you define an abbreviation more than once with the tag?

4 Answers4