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About Stemming

Stemming is a process which reduces words to their stem, base, or root form. The Coveo Platform uses the stem of each queried term to expand the query by searching for the original term and related terms that share the same root. This important automatic query expansion process often helps to find what you are looking for by returning more relevant results that would not appear otherwise.

Note: Stemming only applies to words with more than four characters.

Example: Searching for a term typed in its singular form returns documents containing the singular and plural form of the term, and vice-versa.

The words search, searching and searched share the same root or stem: search-. When you query searching, the Coveo Platform returns documents containing the words searching, search, searches, and searched.

The returned documents containing the original form of queried terms are however ranked higher (see Understanding Search Results Ranking).

Tip: While expanded queries are generally useful, you can disable the stemming expansion when you want to search a specific term or phrase (see Searching an Exact Term and Searching a Phrase).

The stemming rules vary from one language to another as a term can yield different stems for different languages.

Example: The term attention can stem to attentio in English and attenti in French.

Even when a term stems to the same root in two different languages, their respective stem class can very well be different. The Coveo Platform overcomes this problem. At indexing time, the Coveo Platform detects and saves the language of each indexed document. When expanding query terms, the appropriate language-specific stemming algorithm is used for each indexed document (see Supported Languages).

Note: Your Coveo administrator can configure which language is used by the stemming process (see Configuring the Culture of a Search Hub With the .NET Interface Editor).

Stemming confusion can also occur when the stemming algorithm regroups words of different nature under the same stem.

Example: In English, the terms university and universe stem to the same root, although they are not related.

The Coveo Platform further minimizes possible stemming errors by calculating a correlation factor between the searched term and every possible expansion. In search results, highly correlated expansions are ranked higher than poorly correlated ones (see Understanding Search Results Ranking).

Note: Stemming applies to free text queries, but often not to field queries (see What Are Field Queries and Free Text Queries?).

Indeed, field queries with the == operator or with a phrase search will not be stemmed. Also, many standard fields are by default in the StemmingIgnoredFields list below, and therefore not stemmed.

@syssource @syscollection @sysuri @sysurihash @syslanguage @syssite @sysfiletype @sysfilename @sysfileextension @sysspauthorid @sysauthorloginname @syssplistitemid @syssplistbasetype @syssplisttype @sysspparentguids @syssprelativelisturi @sysspsiteguid @sysspsitetruncatedguid @sysspsiteuri @sysspitemtype @sysspiscontainer @sysspispersonalsite @sysspistoplevelsite @sysspsitename @sysyear @sysmonth @syssplistguid @sysspblogpostid @syssplistitemguid @sysspparentname @sysspparenttruncatedguid @sysparents @syssplisttruncatedguid @sysfrom @sysauthor @sysmailbox @sysspcontenttype @sysemailfolders @sysdisplayfrom @systo @sysdisplayto @sysdisplaycc @sysrecipients@sysdisplayrecipients @syscc @sysconversationsubject @sysconversationsubjectid @sysfollowupaction @sysparticipants @sysdisplayparticipants @syscflabels @syscfspacename @sysfolders @sysdesktopconnectorhostname @sysdesktopconnectorversion @sysbcc @sysdisplaybcc @syscsitemtype @syscscommunity @syscstaskassignedto @syscstag @syscstaggroup @sysattachmentdepth @sysconnectortype @syswcmid @syswcmtype @syswcmlibrary @syssfcaseid @syscrmaccount @syscrmaccountid @syscrmaccountstatus @syscrmaccounttype @syscrmasset @syscrmassetstatus @syscrmbillingcity @syscrmbillingcountry @syscrmbillingpostalcode @syscrmbillingstate @syscrmbillingstreet @syscrmcaseid @syscrmcasepriority @syscrmcasestatus @syscrmcity @syscrmcontact @syscrmcountry @syscrmcurrency @syscrmdivision @syscrmindustry @syscrmopquality @syscrmopsalestage @syscrmopsource @syscrmopstatus @syscrmoptype @syscrmowner @syscrmpostalcode @syscrmproduct @syscrmshippingcity @syscrmshippingcountry @syscrmshippingpostalcode @syscrmshippingstate @syscrmshippingstreet @syscrmstate @syscrmstreet @syscrmwebsite @sysrowid @syscsplace @syscsplacetype @syssfcasenumber @syssfcloseddate @syssfcontact @sysdatebucket @syssfcreateddatebucket @syssfclosedatebucket @syssfowner @syssfstatus @syssfpriority @syssfproducts @syssfcreateddate @syssfOpenDate @syssfCaseCallStacks @syssfCaseBugNumbers @syssfCaseHasBugs @sysmiddlename @sysfax @syslnform @systargetfileext @sysspdocsetguid @sysspdocsetname @syssptagnames @syssptagguids @sysinreplyto @sysmessageid @sysconversationreferenceid @sysworkemail
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