So here’s the thing
My dear darlings
About ‘s

It’s used to mean two things,
As you’ve likely guessed

The first use is possession
When the owner’s only one:

Mama’s laugh
Train’s smokestack
Sarah’s yearslong wait

Sis’s birthday
Chris’s workday
James’s rollerskate

The next use is contraction
Combining two words into one:

There’s your half
She’s on track
It’s stuck there in the grate

That’s today
He’s gone away
Let’s no longer date.