/ My Polish girlfriend checks my mobile phone all the time
I don't think that trust is a complicated word. Infact it is one of the most simplistic.
It simply means that you believe in the reliability of that person, how can this be complicated
Don't be so naive Santander, trust is a false and highly dangerous word. Why do you think we have prenuptual contracts, divorce courts, commercial, civil, labour and mecantile contracts and thousands of other contractual agreements on a daily basis...because nobody can be TRUSTED. How many families have broken apart on trust, marriages, businesses, governments, wars (really serious) etc.
May be the word should be "good faith" and up to a point; "I have good faith in my husband or my wife", that sounds better, no? Trust is as only as good as the person who's prepared to believe in it's consequences and they are few and far between. You would be a fool to trust 100% the reliability of someone you love. Your heart wants to but your head says no. That's why some people look at their partners mobile. Just ask any man who has been taken to the cleaners by his ex....."but she was such a loving wife until she met the window cleaner, I trusted her impecably" Now the window cleaner has a new Mercedes, with who's money??? lol. How many women are left holding the baby while HE is off with a younger one.
Don't get me wrong, trust is extremely important in any relationship but it is not SIMPLISTIC