Function stem_word 

pub fn stem_word(word: &str) -> String

The stem an English word is matched by: its plural, its participle and its “-ing” form reduce to the word a description most likely spells (“drawing” and “draw”, “dragging” and “drag”, “scrolling” and “scroll”, “signed” and “sign”). An inflection is only undone when what is left is still a word of reasonable length, so “ring” and “thing” keep their own letters rather than becoming “r” and “th”.