AND

Selects documents that contain all of your search elements. Documents retrieved using the AND operator are relevance-ranked.

To select documents which contain stemmed variations of the phrase "pharmaceutical companies" and stemmed variations of the word "stock", you can enter the following:

pharmaceutical companies AND stock
AND (pharmaceutical companies, stock)

Only those documents that contain both search elements, or stemmed variations of them (for example, "pharmaceutical company", "stocks" etc.), are retrieved. A calculated score is assigned to each retrieved document.