I think it may be more like Pink Unicorn said.."THIS One".

I believe sort of in the "one" myth. Insomuch as that somewhere in all the world there is a preferred gender/ethnic traits/physical appearance individual in my age group that has all the compatible traits, life experiences and similar upbringing that makes them not so much my clone but my perfect foil, best friend, sex partner, etc.
But I am a realist enough to know that with so many unique individuals in the world...they may never cross my path.
I will never allow myself to "settle". But making adjustments to the childhood ideal is quite alright. My physical ideals I can slide on(hair color-height).
I also think that both have to feel that the other is "the One" to fit the definition ^_^

My first "one" I moved too far from in the pre internet days. The person I feel was THE "One" was killed tragically mere months after finally coming out of friend zone to tap hard on my shoulder in 1989; we had known each other 11 years.
Hunny was very much like number two.While we were friends he had the comfortable fit of favorite jeans. It seemed like there never was a time we were not friends. Ironically when I finally saw his appearance(which he was shy of. NO social media ANY where has his image until his recent Facebook) he even looks like him though about 4 inches shorter.

The one for my definition; is the man who likes me as much as he loves me, so enjoys long periods of time in just my company. Shares some hobbies, tries new things for me (and vs). Is happy to see me and enjoys eating across table from me. Can hug me for my traits that are not his favorites while kissing me over those that are. Wants me for me. Just the way I am.

And hopefully healthy enough socially to have type friends that he can say to honestly with smile "sorry guys, my lady and I had plans this Saturday", and can easily and comfortably ask me "Hey Kochanie, next Saturday the guys wanna go do"x" with me. If we have no plans I am going." And...well I won't complain if the after dark schedule is working as intended.