Faith is the noun form of the word, to believe.
Faith is the substance of things hoped for, the evidence of things not seen, Hebrews 11:1.
Faith is the confidence, the belief, the trust in someone or something that is supported by claims and evidence (regardless of the veracity of those claims and evidence) that a person or thing can do or be what the claims and evidence demonstrate. Having faith in an object doesn't produce capability, the object is inherently worth trusting in based on the claims and evidence made by/of the object.
Faith is not a verb or noun that specifically pertains to spiritual things, or things of a spiritual nature, like one can have faith that a chair will support one's weight, or that a car will enable you to get from point A to point B without failing. But in the context of a biblical application of faith, it demonstrates that it is followed by a work of the Holy Spirit, Who neither forces faith nor is ineffectual in the way that it is distributed. The activity of the Holy Spirit is present as faith grows, and supports a person's faith journey when a person submits/humbles themselves to the Holy Spirit's work in their life.