Writing vocabulary definitions

Don't write a negative definition (e.g. this does not include, this does not mean)
The term and the definition should be interchangeable in a sentence
Avoid circular definitions (e.g. evergreen tree - tree with evergreen foliage)
Don't be too broad or too narrow
Use only one sentence
Be aware of broader terms
Terms should be nouns (person place or thing) and should be described as nouns
When appropriate, attribution should be given
Use words appropriate to the intended audience level (e.g. 'lifted condensation level' as a scientific term and 'cloud level' as a more generic term)
If the audience range is large, use more generic words rather than specialized ones

From the Open Forum on Metadata Registries, January 2003.