The template {{glossary}} (a.k.a. Template:Tnull or Template:Tnull) is used with {{glossary end}} to explicitly bracket a glossary or glossary-like description list (also called a definition list or association list), especially in a template-structured glossary, although such lists can be used more generally. This is required (as a technical matter) for template-structured glossaries, and is good practice anywhere description/definition lists are used for glossaries. The template pair invoke the <dl>...</dl>description listHTML element. Unfortunately, the "Template:Tnull" mnemonic is not available as a redirect as of this writing.
The pair of templates incidentally prevent Wikipedia's MediaWiki software engine from auto-creating redundant definition list code (<dl>...</dl>) around terms and definitions if they have blank lines between them, as they often do, especially in non-structured glossaries.
|id= can be used to assign a one-word ID name to the glossary. This can be used as a #id link target, and could have other metadata uses.
|style= will pass CSS styling on to the <dl> element. I.e., this styles the definition list itself, as a container, not the individual terms and definitions with it. There is rarely any reason to do this.
|class= will pass one or more space-separate CSS classes on to <dl> element, in addition to the automatically included class glossary. There is rarely any reason to do this.
Examples
This shows both a very simple then a rather complex instance in a structured glossary (including an entry with a block quotation, which inside a definition has reduced vertical margins compared to the standard display of {{blockquote}}, due to TemplateStyles):
Markup
==A–M=={{glossary}}{{term|1=applesnorkel}}{{defn|1=Definition of term 1.}}{{term|term=arglefarst |content={{lang|xx|arglefarst}}{{anchor|argle-farst|argle farst}}}}{{defn|no=1 |defn=Beginning of first definition of term 2
{{blockquote|1=Block quotation in first definition of term 2.}}
Conclusion of first definition of term 2.
}}{{defn|no=2 |defn=Second definition of term 2.}}{{glossary end}}
Renders as
A–M
applesnorkel
Definition of term 1.
arglefarst
1. Beginning of first definition of term 2
Block quotation in first definition of term 2.
Conclusion of first definition of term 2.
2. Second definition of term 2.
Scope
This family of templates, like the underlying definition-list code, is primarily intended for definitional uses, but can have other applications. The HTML 4.01 Specification itself says:
Definition lists ... generally consist of a series of term/definition pairs (although definition lists may have other applications). Thus, when advertising a product, one might use a definition list:
Lower cost
The new version of this product costs significantly less than the previous one!
Easier to use
We've changed the product so that it's much easier to use!
Safe for kids
You can leave your kids alone in a room with this product and they won't get hurt (not a guarantee).
— Source
Thus, editors should feel free to use definition-list markup as an alternative to bulleted or numbered lists when the material is well-suited to definition-list presentation.
