The following recommended philosophy books are secondary, single author books accessible to advanced undergraduates and philosophy majors. They provide an excellent introduction to the basics. A few of these are a bit dated, but those that are are extraordinarily clear and still useful. A supplemental update volume has recently been published. There are some true dictionaries of philosophy out there, but I wouldn't recommend any of the ones I have read.
Philosophers are fond of adding their own shades of meaning to common philosophical terms.
The series is a bit uneven. For example, The Blackwell Companion To Epistemology , edited by Ernest Sosa and John Greco, is excellent, but the volume devoted to ethics is quite weak.