See Hebrews 11:6. So what is faith? Perhaps a great way to narrow down the true Biblical definition of faith is to begin by stating what faith is not. Faith is not a force, a formula, a form of religion, a feeling or a fortune.
The Bible actually gives us a very specific definition of faith and then some examples of what it looks like in real life. See Hebrews 10:38–39; Hebrews 11:1.

Faith: Confidence God is and will do what He promised to do.

We don’t believe in God or His promises because of faith. We believe God is and that he keeps his promises because of evidence. The writer of Hebrews gives us the evidence…from creation, from the ancients, from those who are being persecuted because of their faith.
See Hebrews 11:2. I want to zoom in on one of the ancients, one of the heroes of the faith — Abraham. See Hebrews 11:8–12.
Why did Abraham do these things? Because God made him a promise. See Genesis 12:1-3; Galatians 3:16; Galatians 3:26-29.
God keeps His promises. They are evidence that He is faithful. The promise all the ancients looked toward was Jesus. The greatest promise that we now look back to and, at the same time, forward to is Jesus. The writer of Hebrews tells us the crucial role that Jesus plays in the faith of His followers. See Hebrews 12:1-2; 2 Corinthians 1:19-20.

Faith is confidence God is and will do what He promised to do through Jesus Christ.

Jesus is all the evidence we need. In the early church, the Apostles always connected faith to the evidence of the cross and the resurrection of Jesus. Read: 1 Corinthians 15:1-20
The death, resurrection, ascension of Christ is the foundation of my faith in God and His promises for me. Your faith is not anchored in some mythical, “once upon a time in a land far, far away” kind of story. Your faith is anchored in the person, Jesus Christ. Example of faith in Jesus (Matthew 8:1-3).
Faith is not based on you, it is based on Christ. True faith leaves the Lord in control. Faith isn’t a force that we use to manipulate God. Faith is a firm confidence in the goodness, the wisdom, and the purposes of God.

The validity of your faith is not based on the results from God, it’s based on your resolve in God.

Some have “lost faith” in God because they had faith, they prayed, and God didn’t answer the way they thought he should. Is that actually faith? See Hebrews 11:39. How could the be commended for their faith if they did receive what had been promised? Because their faith was not in getting from God, their faith was trusting in God — His plans and purposes; His grace and His goodness.
Faith is confidence God is and will do what He promised to do through Jesus Christ. What is the greatest promise you can and will receive through faith? Your salvation. See Romans 5:1-2.
Faith in God is best demonstrated through obedience to God.