Definition
A new commandment I give to you, that you love one another, even as I have loved you, that you also love one another. BY THIS ALL MEN WILL KNOW that you are My disciples, if you have love for one another.
John 13:34 & 35
Know – ginōskō(verb) (G1097)
- to learn, to know, come to know, get a knowledge of perceive, feel
- to become known
- to know, understand, perceive, have knowledge of
- to understand
- to know
One Another Living 
Definitely one of the ways to know a believer in Christ is authentic!