Today we hear the end of Jesus's discussion with Nicodemus and we arrive at what has become a common term in so parts of Christianity. born again. Among our Evangelical brothers the term has taken on a particular meaning, but we Catholics also understand the term in the simplest biblical sense.
Here John uses a word that has been translated as "again" but literally means "from above" (anothen) from (ano) which means up, on top, on high. Many, even the newest King James bible has made this correction. In Verse 5 Jesus goes on to explain that this means that one must be born "of water and the Spirit" and unless one is born of water and the Spirit they cannot enter the Kingdom of Heaven.
For us this second birth happens in baptism. Like our first birth it is not something we do, but something that happens to us by God's grace. In the waters of baptism we are reborn. This understanding of Jesus's words can be traced back to the earliest available writings on this passage. The Catholic, Orthodox, Lutheran, and Anglican communion are all in agreement as to the interpretation of this passage. Only our Evangelical brothers and sisters have attempted to link this passage from John's Gospel with Romans 10 and thereby link being "born again" with a verbal profession of faith on the part of the individual.
So if you are a Catholic and someone asked if you have been born again, you should answer with a resounding yes. On the day of your baptism have no doubt that "through water and the Holy Spirit" you were born from above (anothen) just as Jesus teaches us we must be in John's Gospel.