title: What is the difference between lower bound and tight bound?
body: <p>With the reference of this <a href="https://stackoverflow.com/questions/3255/big-o-how-do-you-calculate-approximate-it#3368">answer</a>, what is Theta (tight bound)?</p>
  
  <p>Omega is lower bound, quite understood, the minimum time an algorithm may take. And we know Big-O is for upper bound, means the maximum time an algorithm may take.  But I have no idea regarding the Theta.</p>