The OR operator | can be used to search for documents about either cats or kitties:

cats | kitties

The AND operator can be used to search for documents about both space and exploration. The AND operator is used by default, but can be made explicit with the & symbol:

space & exploration

The NOT operator - or ! can be used to exclude documents about landscapes when searching for Vista:

Vista -landscape

You can surround phrases in quotes ", for instance to search for famous quotations:

shakespeare "to be or not to be"

You can use the proximity operator ~ to search for a group of words within a certain distance of each other. For instance, to search for the words "Saturn", "rings", and "size", all within a span of less than 10 words:

"Saturn rings size"~10

The quorum operator / can be used to do fuzzy matching. If you would like to find documents that have at least three of the five words "college", "university", "learning", "study", "library":

"college university learning study library"/3

OR operator precedence is higher than AND, so looking for cat | dog | mouse means looking for ( cat | dog | mouse ) and not (looking for cat) | dog | mouse.

Important note on parentheses: You can use parentheses to override the normal precedence order; however, nested parentheses are not allowed. The NOT operator cannot be used within parentheses, only at the top level.