Greetings and Blessing be upon you in the name of our Lord Jesus Christ.
Great Question Rochir! I am glad you asked this question.
I would like to say, to define anything in one world, even a single word, needs more then one word to define it, but If I was to sum up, most of, or the very basis premise of Christnaiy to me, in one word I would have to say that word would be:
Life
Now, this might need some explaining, because many people said love, or faith, and many other great ones, and I have you all know, I agree with you, Christianity is love, faith, devotion, and many other things. All of everyones answers were Good and I want to say you are all correct.
Let me explain why I say Life:
To me the Christian faith is about how to live a good life, where you have a personal relationship with your creator, your given a purpose and your worries are removed, Christianity is the path to a life filled with Love, Devotion to God and family. Its about having a life free of the many burdens we have to cope with.
Christianity is a religion that gives you lifes instruction Book on how to live a good life and die a good death here on earth, and live for Eternity in the hear after with your creator, to see the universe, its mysteries unfold before your eyes. To know life to the fullest.
That is why it called being Born Again, to renew a life, an eternal life.
But this is just my opinion.
God Bless.
Vigil.
Be sober, be vigilant; because your adversary the devil, as a roaring lion, walketh about, seeking whom he may devour: (1 Peter 5:8)