Today we examine two related words, both of which appear extremely often in the New Testament (about twice in every chapter, on average). They are pistis (PIS-tis) and pistos (pis-TOS). The basic sense of pistis is "faith, trust, and belief." Note: faith and belief are synonyms -- there's no real difference in meaning. Of course we are not justified by empty faith (James 2), but rather by faith with content, faith with heart.
The second word, pistos, means "faithful, trustworthy, reliable" but can also occasionally mean "believing." (Note: In Titus 1, the somewhat controversial "eldership" passage about children, modern translations favor "believing" as the translation, but either alternative is possible.) In addition, in the LXX (the Greek version of the Old Testament) these words are found hundreds of times. What an enormous biblical theme!