Faith is Trust

See Also My More In depth Look at the Meaning of Faith

Pistis the noun
Pistis is the Greek noun usually translated "belief" or "faith." There is variation among Christians as to its meaning. To some, pistis merely means "mental acknowledgment," others recognize that pistis usually includes "confidence" or "action." Still others define it differently. Unfortunately, the usage of the words "belief" or "faith" in every-day English is too vague to accurately translate pistis in the New Testament.

Pistis is best translated as the noun trust.

Pisteuo the verb
Pisteuo is the Greek verb usually translated "believe." The word "believe" means to accept information as being true, but it is not personal and does not necessarily include action.  Therefore, "believe" is inadequate to translate pisteuo.

Pisteuo is best translated as the verb trust.
The Greek verb for trust is translated most often as believe. The Greek noun for trust is translated most often as faith. So when scriptures say believe it means have faith or most clearly "trust."

Believing is often thought of as impersonal, distant, and unsure. Trusting is personal and confident. There are plenty people who "believe" the facts of the good news but by no means trust the person of Jesus interactively. Belief is something I think. Trust is what I give to someone else.

How the Translation Impacts our Understanding
Believe is a short sighted word that usually stops at "thinking a fact to be true." So when John 3:16 says whoever "believes in Him" it renders best to whoever "trusts in Him." Trust holds a lot more weight than belief.
So knowing that the Greek word  for "believe" clearly means "trust" lets look at some scriptures:

The one who believes in the Son has eternal life.
The one who trusts in the Son has eternal life.
Already we have something much more personal and real regarding God. You can "believe in" something that is not real or something you have never encountered. Trust is present, real, and personal.

I tell you the truth, whoever hears my word and believes him who sent me has eternal life and will not be condemned.
I tell you the truth, whoever hears my word and trusts him who sent me has eternal life and will not be condemned. What is Jesus talking about? Regarding the Father as simply truthful or trusting Him interactively? See how much meaning is lost here?

For just as the body without the spirit is dead, so also faith without works is dead.
For just as the body without the spirit is dead, so also trust without works is dead.
This reaffirms the definition of the Greek word. Hebrews 11:8 says "By pistis (trust) Abraham, being called, obeyed to proceed to a place which he was about to receive for an inheritance, and he went out, not knowing where he was going." Abraham not only accepted what God told him as being true, but also had enough confidence in it to act upon it (Abraham obeyed). Hebrews 11 shows us that faith is not an unclear mystical idea. Faith is trust. Who do you trust?

Even with trust being the best translation belief could be translated in place of the word faith because it is the noun form of believe.
For just as the body without the spirit is dead, so also belief without works is dead.

So faith/belief/trust is interactive confidence, security, in God and His truth that results in action according to His truth. If you "believe in/trust in" God that means you know and love God.

The language itself (perhaps not by anyone's fault in this case except that faith is a more religious word than trust) hides the meaning of true salvation and it makes it about what I hold in my head (belief) rather than WHO HOLDS MY HEART IN HIS HAND because He is my life. Trust in God means you are entrusting Him with your very self. Trusting God is like trusting your mother, father, spouse, or best friend. Biblical belief, biblical faith, biblical trust then is not an idea that you hold to be true. It is a spiritual relationship with God based on trust. You trust God like you would any human. You trust that God is trustworthy, worthy of trust, and you live like it.

All these things line up with context of scripture. It is surprising how true meanings of the words convey the scriptures so well and make it that much clearer and bolder. I encourage you to read the scriptures knowing that "to believe" means "to trust" and that "faith" means "trust." I pray that it will give you greater insight into the heart of Christ as it has for me. God wants us to know Him as living, loving, and local not dead, detesting us, and distant.

See also:  My More In depth Look at the Meaning of Faith. & My look at the term believer.
Read more about the meaning of the word trust in scripture.

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English Etymology
Belief used to mean "trust in God," while faith meant "loyalty to a person based on promise or duty." Faith took on the religious sense beginning in 14th century translations. Belief had by 16th century become limited to meaning "mental acceptance of something as true."

Current English dictionary definitions.
Believe
To be persuaded of the truth of, upon evidence furnished by reasons, arguments, and deductions of the mind, or by circumstances other than personal knowledge
to regard or accept as true
to place confidence in
to have a persuasion approaching to certainty
to hold an opinion : think
to consider to be true
to hold as opinion

Believe in
have a firm conviction as to the goodness of something; "John believes in oat bran"
To ascribe existence to; To ascribe some powers or other attributes to
To believe that the subject of the thought (if a person or thing) exists, or (if an event) that it has occurred, or will occur; - as, to believe in the resurrection of the dead.
To believe that the character, abilities, and purposes of a person are worthy of entire confidence; - especially that his promises are wholly trustworthy.
To believe that the qualities or effects of an action or state are beneficial: as, to believe in sea bathing, or in abstinence from alcoholic beverages.

Faith
Confident belief in the truth, value, or trustworthiness of a person, idea, or thing.
Belief that does not rest on logical proof or material evidence.
Loyalty to a person or thing; allegiance
strong or unshakable belief in something, esp without proof or evidence
complete confidence or trust in a person, remedy, etc.
Mental acceptance of and confidence in a claim as truth without evidence supporting the claim.
A feeling or belief that something is true, real, or will happen.
A trust in the intentions or abilities of a person, object, or belief in spite of a lack of knowledge in the person, object, or belief.

Belief
Mental acceptance of a claim as truth regardless of supporting empirical evidence.
conviction of the truth of some statement or the reality of some being or phenomenon especially when based on examination of evidence

Trust
To place confidence in; to rely on
Assured reliance on the character, ability, strength, or truth of someone or something
To rely on the truthfulness or accuracy of
To give credence to; to believe; to credit.
To hope confidently; to believe