Faith

The dictionary defines the word "faith" as the following:

1. confidence or trust in a person or thing.
2. belief that is not based on proof.
3. belief in God or in the doctrines or teachings of religion.
4. belief in anything, as a code of ethics, standards of merit, etc.
5. a system of religious belief.
6. the obligation of loyalty or fidelity to a person, promise, engagement, etc.
7. the observance of this obligation; fidelity to one's promise, oath, allegiance, etc.
8. Christian Theology. the trust in God and in His promises as made through Christ and the Scriptures by which humans are justified or saved.
~Dictionary.com Unabridged (v 1.1)Based on the Random House Unabridged Dictionary, © Random House, Inc. 2006.

The following is what the Bible says:

"Now faith is being sure of what we hope for
and certain of what we do not see."
~Hebrews 11:1

Let's take a moment to expound on this verse. The word "sure" is an absolute word, which means to say: "complete conviction", "doubtless", "fully convinced and persuaded".

Following that, the object that we are "being sure" of is "what we hope for". "what we hope for" is something that is not perceived by our senses, and that's why that something is "hoped for". The word "certain" is another absolute word, which carries similar meaning as the word "sure" with the underlying sense of "destiny".

I notice that the Bible defines it starting with a present continuous tense using the word "being". In other words, it carries the meaning of the state of progress or existence. From another perspective, it also implies an ongoing process that takes place.

In Christianity, we are called to "faith" in Jesus Christ.
In parallel, it means:
"Being sure of what we hope for and certain of what we do not see" in Jesus Christ.

No christian alive would be able to say the above statement with a 100% surety and confidence because
"... he who began a good work in you will carry it on to completion until the day of Christ Jesus."
~Phil 1:6

So brothers and sisters in Christ, let us not be surprised when doubts surround our heart and mind but instead
"... Let us fix our eyes on Jesus, the author and perfecter of our faith ..."
~Hebrews 12:2