Am in the military, i've seen so many tragic events.. i know how faith has kept me, thats why i 'm being part of this discussion..
Faith is believing in what is true. Faith has two elements: 1) being convinced of the truth, being certain of reality, having evidence of unseen things, and 2) believing, hoping in, embracing, seizing the truth.
Heb 11:1 (KJV) Now faith is the substance of things hoped for, the evidence of things not seen.

Heb 11:1 (NIV) Now faith is being sure of what we hope for and certain of what we do not see.
While faith requires being convinced that what we believe in is true, just knowing the truth is only half of faith. God's word must be hoped for, embraced, seized!
Luke 17:5 (NIV) The apostles said to the Lord, "Increase our faith!" He replied, "If you have faith as small as a mustard seed, you can say to this mulberry tree, 'Be uprooted and planted in the sea,' and it will obey you."

Believing is not exactly the same as faith. For belief to be faith, it must light on what is certainly true. Yet Scripture gives examples of situations where belief alone is required, even commanded. There's no time for evidence collection, to wait, to hear, for certainty. Just believe. Like Peter walking on the water--don't think, act! God even requires us to believe in him when, temporarily, the evidence looks bad: to trust. [We will study belief and trust separately.] God requires belief and trust in moments of human weakness, but faith is what makes us strong. Faith is the state of being convinced about what we hope for.