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NorwegianSnowballStemmer.Stem

The Snowball stem of one Norwegian word.

public static string Stem(string word)

Parameters — word is a single Norwegian Bokmål word. It is lowercased and NFC-normalised before the rules run, so a decomposed å and a composed one are the same letter to the algorithm.

Returns — string, the stem, always lowercase, and still carrying whatever æ, å or ø the input had.

Exceptions — ArgumentNullException when word is null. An empty string, or a word of one character, is returned lowercased and otherwise untouched.

Example — a participle rewritten rather than stripped, and a consonant pair losing its t.

using Lodestar.Text.Stemming;

string participle = NorwegianSnowballStemmer.Stem("servert");  // => server
string past = NorwegianSnowballStemmer.Stem("serverte");  // => server
string neuter = NorwegianSnowballStemmer.Stem("halvt");  // => halv

Remarks — mulighet → mul is the result most likely to look like a bug, and it is two steps rather than one: het goes in step 1, which uncovers mulig, and ig then goes in step 3. The algorithm has no dictionary to tell it the remainder is not a word, and it does not need one — mulighet, muligheten and mulighetene all reaching mul is exactly the point.

using Lodestar.Text.Stemming;

string noun = NorwegianSnowballStemmer.Stem("mulighet");  // => mul
string definite = NorwegianSnowballStemmer.Stem("muligheten");  // => mul
string plural = NorwegianSnowballStemmer.Stem("mulighetene");  // => mul

The bare s is the other rule worth knowing, and the only one that inspects a letter outside R1. It is removed only after one of eighteen letters, or after a k that is not itself preceded by a vowel. That last clause is what parts two words that look alike:

using Lodestar.Text.Stemming;

string genitive = NorwegianSnowballStemmer.Stem("folks");  // => folk
string noun = NorwegianSnowballStemmer.Stem("boks");  // => boks

folks has an l before its k, so the s goes; boks has an o, so the s stays and the word is its own stem.

Applies to — net10.0, netstandard2.0.

See also — NorwegianSnowballStemmer, the stemming index.