Web search engines today are very adept at picking up word variants; ie different forms of a word, especially singular and plural forms. Google and Bing will also return some results that have synonyms to our search terms – largely based on statistical co-occurrence.
For example, for the query Scotland Canada emigration , Google and Bing deliver results with the words bolded for emigration, emigrants, emigrated, emigrating as well as the related words, migration and immigration. Both engines will also identify Scots, Scotland, Scottish.
Usually pages that have all these terms will be more relevant for you. But sometimes they may introduce false leads. Always watch for the bolding of terms in the search results, and then decide on the words you really want to use. For greater control you could switch to Boolean – this turns off word variants – Scotland Canada (emigrants OR emigration).
At Google, we used to be able to use the synonym operator – tilde (~) – to request related words. That syntax operator was dropped in 2014.
[Updated May 7, 2015]