Pistis is the transliteration of the Greek term translated in the KJV as "faith" Pistis is formed from two roots, "Piq" meaning bind, and "tis" having the same function as "er" in English. So fundamentally, the Greek term means "binder" or that which binds. Now lets look at how the Bible defines the term contextually. Hebrews 11:1, "Now faith is the substance of things hoped for, the evidence of things not seen." The word translated "substance" comes from the Greek hupostatis, which means "under" "stand" having nothing to do with comprehension, but rather with what undergirds what we stand for. So "faith" is what undergirds our hope for the realization of the promises of God. The next word of interest, "evidence" comes from the Greek elegchos, which means that which brings to light what is not easily seen. For example, in 2 Timothy 3:16, the AV translates it "reproof" indicating scripture is profitable because it brings to light our sins. In summary, Faith (Pistis) refers our heart-felt conviction that Jesus is the Son of God and the Messiah sent from God, and this conviction binds us such that our subsequent attitudes, hopes and deeds are tied to the reality of Jesus as our Savior. As Paul liked to say, referring to Habakkuk, the righteous man lives by faith. Do we live like someone indebted to the one who saved us, a bondservant of Christ, or like some ungrateful twit?