Sonder

 “Sonder” is a noun popularized by writer John Koenig in The Dictionary of Obscure Sorrows. It means:

The realization that every random passerby is living a life as vivid, complex, and emotionally rich as your own.

It describes that sudden awareness that strangers each have:

• their own memories,
• routines,
• fears,
• relationships,
• ambitions,
• heartbreaks,
• and inner worlds you’ll probably never fully know.

Example:

Sitting in traffic and realizing every car around you contains someone with an entire life story — that feeling is sonder.

The word isn’t an old dictionary term; it was coined in the 2010s, but it became widely used because it captures a very recognizable human experience.