Loyalty is built off of the previous law of trustworthy. Similarly it is gained and earned over time, but once it is achieved, loyalty is normally an unshakable force.
Again using the Merriam-Webster online dictionary loyal is defined as, having or showing complete and constant support for someone or something.
Loyalty takes on many forms to always supporting your favorite team even if its been decades since a shot at the championships. ( Chicago Cubs) Some people are fiercely loyal to specific brands or companies sometimes willing to pay a little extra for that product or service because it has been consistently what they want or need. Loyalty could also be given to a specific person or persons.
It is on this last part that some caution needs to be taken. In the same fashion that once trust is lost its dam near impossible to get back the same can be said for loyalty. This should be understood in both personal and professional relationships.