You want to find all occurrences of the expression to go berserk in your corpus.
Would a search for "go" followed by "berserk" give you the results you expect? Think about it, then click the button below.
No, it would probably give you fewer results than are available in the corpus.
You have certainly guessed why: a search for "go" and "berserk" would fail to find occurrences of goes berserk, went berserk, gone berserk and going berserk.
Since this expression is not very frequent to start with, you need to maximise your output!
Having worked through unit 2 in section 1, you will remember that a computer operating with plain text files is not able to merge all word forms belonging to a given lemma into one single entry. You need a specialised software to lemmatise your corpus, i.e. a lemmatiser.
Summing up:
If you want to search for a noun in both the singular and the plural, or a verb regardless of its tense and person, you can either:
search for the lemma (if the corpus is lemmatised)
search for all the forms (if the corpus is not lemmatised)
You can use regular expressions to search for all the forms of a given lemma in a single query.
Test yourself
To which lemma(s) would you assign the word "left" in sentences 1 and 2 below?
Stay on the left side of the ramp.
Elvis has just left the building.
both to the verb lemma LEAVE
both to the adjective lemma LEFT
"left" in sentence 1 to verb lemma LEAVE, "left" in sentence 2 to adjective lemma LEFT
"left" in sentence 1 to adjective lemma LEFT, "left" in sentence 2 to verb lemma LEAVE
Don't go berserk!
Test yourself