Use the truncating symbol -- an asterisk * -- to look for various word endings. For example:
controvers* -- Notice the * (asterisk, or shift + 8) replaces the y. It will look for all these variations:
controversy
controversies
controversial
The example demonstrates searching climate change and controvers*:
Use quotation marks to keep two or more words together in a phrase. For example:
"climate change"
"global warming"
"arguments against"