A metalanguage is a language used to make statements about statements in another language which is called the object language. It can refer to any terminology or language used to discuss language itself. In UNL, the representation of metalinguistic statements are to be differentiated from linguistic statements by the attribute @mention, which normally corresponds to the use of italic or quotation marks in natural language:
- Cheese is derived from milk
- "Cheese" is derived from a word in Old English = cheese.@mention
The first sentence is a statement about the substance called cheese; it uses the word "cheese" to refer to that substance. The second is a statement about the word cheese as a signifier; it mentions the word without using it to refer to anything other than itself and should therefore be associated to the attribute @mention.