Capital letters in this situation?

[MistletoeAndTomHardyPlease]

If you are referring to someone as something do you use a capital letter?

For example if you were calling someone darling?

'will you step over there please, darling?'

Would the darling be 'Darling'?

I just need to check please!

[MistletoeAndTomHardyPlease]

Bump!

[ElphabaTheGreen]

I would say no, as it's not technically a proper noun, more of an adjective.

If I saw 'darling' used as you describe capitalised in a book it would look odd to me.

[MistletoeAndTomHardyPlease]

Thankyou!

[ScienceRocks]

No. Definitely not.