TRUST

What is trust?  What gives it meaning?  I ponder things like this at times.  It seems to me that trust is the foundation of my relationships, yet I have never taken the time to define it.  Do I just assume it to be there?  When young, I trust my parents.  I depend on them to provide for my needs so I may live.  So, is this trust, or mere dependence?  Does trust require a choice, a condition of "non-trust" as an option?  If this is the case, my example of my parents would not be considered trust, I would think.  As I grow into adulthood, I realize trust plays more of a role in my relationships.  Maybe trust is directly proportional to my openness to another?  A casual meeting requires little trust.  But when I drive my car, I must trust the other driver to follow the same rules of the road as myself.  Is this the same trust as in an intimate relationship?  Maybe there are different forms of trust, such as different types of snow?  Maybe the problem with trust is that there is no one definition.  Maybe trust is an expression of one's personality.  Does the trust of an introvert differ from that of an extrovert?  I believe myself to be an extrovert.  I believe I assume trust in a relationship, then am surprised when my "trust" is shattered by behavior I deem unacceptable.  Is this putting undue burden on those I befriend?  How can "lines of trust" be delineated at the onset of a relationship so all involved agree what is acceptable versus non acceptable behavior?  Or does behavior have nothing to do with trust?  Maybe I place too great a burden on the other in my relationships.  Maybe I must limit my trust to myself.  What am I prepared to express with no concern for repercussion?  I trust the answer will come to me.  I trust my relationships in the future will not crumble because my definition of trust is not in sync with those I care to share myself with.  Or, maybe I am over-thinking the issue?