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.

Typical usage:

{{glossary}}
{{term}}
{{defn}}
{{glossary end}}

• |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.

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):

==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}}

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).

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.

• {{glossary}} a.k.a. {{glossary start}} or {{glossary begin}} – Half of a template pair; uses <dl> with a class to open the structured glossary definition list that {{glossary end}} closes.
• {{glossary end}} – The other half of this template pair; uses </dl> to close the definition list that {{glossary}} opens.
• {{term}} – The glossary term to which the {{defn}} definition applies; a customized <dt> with a class and an embedded <dfn>.
• {{defn}} – The definition that applies to the {{term}}; uses <dd> with a class
• {{ghat}} – a hatnote template properly formatted for the top of a {{defn}} definition
• {{glossary link}} – meta-template for creating shortcut templates for linking to definitions in specific glossaries
• Wikipedia:Manual of Style/Glossaries