You may combine search words with OR, AND and NOT. AND-expressions are evaluated before OR-expressions. Words are ANDed togeth by default. Hence sinclair duck is equivalent to sinclair and duck.
For instance the search expression londo AND g'kar OR delenn will find all documents containing both Londo and G'Kar, plus all documents containing Delenn. You may also write this as ( Londo AND g'kar ) OR Delenn.
The search expression Londo OR Sheridan AND NOT G'Kar will find all "; documents containing Sheridan and that do not contain G'Kar, plus all documents containing Londo. You may also write this as Londo OR ( Sheridan AND (NOT G'Kar) ).
You can search for partial words by truncating them with *, for instance Vorl* will match all words beginning with Vorl. Note that this is also useful for getting plurals and possessives of words, so sinclair will not find sinclair's duck nor will it uncover the sinclairs have always been pilots. But sinclair* will find both.