BIPM metrology portal

Widening your search

Prefix search

Prefix search allows you to find documents based on the beginning of a word. This operator allows for instance, to find a proper noun from its shortened version, or to search on the linguistic root of a word.


Searches for documents containing words starting with Jenn: Jennifer, Jennie, Jenni, Jenna, etc.


developing, developed, development, develops, etc.

Optional terms

The OPT operator allows you to specify a term without making its presence mandatory for a document to appear in the search results. Use it to specify several terms so as to make the search more precise, without narrowing it.

cow OPT mad

Search for documents containing "cow" with preferably "mad".

Alternate terms

OR allows you to specify several disjunctive terms. This means that the search engine will retrieve any document that contains either one term or the other. For example, use it to specify a list of similar terms that may occur in the type of document you are looking for.

(movie star) OR (famous people)

Searches for documents containing either movie star or famous people.


Exalead supports regular expression patterns. Patterns are introduced by a slash ('/') character. Within a regular expression, '.' is a special character that can represent any character, '*' stands for character repetition, '|' stands for 'or', and parenthesis are used to group characters. '?' is placed the end of a character group to make it optional.


Searches for documents with words that match the pattern S . R EN .. PI . Y -- this can be very useful to finish your crossword puzzles!


Searches for documents containing any of the following: mpg, mpg1, mpg2, or mpg3.
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