Should you define an abbreviation more than once with the <abbr> tag?
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29-10-2019 - |
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?
Solution
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.
OTHER TIPS
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 anchor
s 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.
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.
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):
- G97: Providing the abbreviation immediately following the expanded form
- G102: Providing the expansion or explanation of an abbreviation
- H28: Providing definitions for abbreviations by using the abbr and acronym elements
- H60: Using the link element to link to a glossary
- G55: Linking to definitions
- G70: Providing a function to search an online dictionary