"X" stands for the unknown in mathematics. Replacing one's name with an unknown number adds infinite laughter and romantic mystery to everyone's guess. In addition to the unknown, "X" has another meaning: kiss. This is mainly because the pronunciation of "X" is similar to that of "Kiss". At the end of letters, emails or cards, many people will write: XOXO. If "X" is "kiss", then "O" is "hug". Don't we always put our arms in an "O" shape when we hug?

As long as we are good friends, whether men or women, we will not hesitate to attach XOXO to the end of an email or card. What better blessing can there be? Although no one talks about it, we all know in our hearts that XOXO makes us feel closer, closer and warmer.