The New Testament Greek word translated "faith" is pistis, the same word also rendered "belief." It basically means "firm persuasion" and "conviction based upon hearing."
Notice the definition from a respected Bible dictionary: "The main elements in 'faith' in its relation to the invisible God, as distinct from 'faith' in man, are especially brought out in the use of this noun and the corresponding verb, pisteuo ["believe"]; they are (1) a firm conviction, producing a full acknowledgment of God's revelation or truth, e.g., 2 Thessalonians 2:11-12 2 Thessalonians 2:11-12  And for this cause God shall send them strong delusion, that they should believe a lie:
 That they all might be damned who believed not the truth, but had pleasure in unrighteousness.
American King James Version×; (2) a personal surrender to Him, John 1:12 John 1:12But as many as received him, to them gave he power to become the sons of God, even to them that believe on his name:
American King James Version×; (3) a conduct inspired by such surrender, 2 Corinthians 5:7 2 Corinthians 5:7(For we walk by faith, not by sight:)
American King James Version×. Prominence is given to one or other of these elements according to the context" (Vine's Complete Expository Dictionary of Old and New Testament Words, 1985, "Faith").
Faith is trusting belief, conviction and conduct based on a right relationship with God. It is not static, but grows in strength and depth as we nourish that relationship with our Creator throughout our lives.