Simple Meaning
Finding something good without looking for it. It's like when you accidentally discover something wonderful that you weren't even searching for.
Common Usage
In everyday life
"It was pure serendipity that I met my best friend at a random coffee shop."
In scientific discovery
"The discovery of penicillin was a case of serendipity - Fleming found it by accident."
In career
"Through serendipity, she landed her dream job after a chance encounter at a conference."
Etymology
Coined by Horace Walpole in 1754, from the Persian fairy tale 'The Three Princes of Serendip', whose heroes were always making discoveries by accidents and sagacity.