Common definition: the condition that distinguishes animals and plants from inorganic matter, including the capacity for growth, reproduction, functional activity, and continual change preceding death.
Technical or philosophical definitions: if you have the time you can read a panoply of opinions at
https://philosophynow.org/issues/101/What_Is_Life
Then we can search deeper and ask also what is the meaning of life? Or how does it come to be in the first place? And for that we have also many philosophical and psychological aspects and hypothesis explanations spread all over since the dawn of our history.
And what does it mean to be alive? Again, there is no general agreement on how to answer this question. But on this brief article, I want just to stick to the living species or if you want how many species can be described as alive (even if it remains to know what being alive really means) on our Earth. Unfortunately, nobody knows even the approximate number.
"Although to this date about 1.5 million species have been formally described in the scientific literature, most of them insects, scientists generally agree that many more species exist than are formally described, but they disagree about how many there really are. Some studies have estimated 2 million or fewer, whereas others suggest as many as 12 million (one recent study even suggested the planet could be home to a trillion species). The most recent pie of life is summarized in the following picture:
https://phys.org/news/2017-08-biodiversity-earth.html
If we think about the millions (I know they are much more than that) of planets that exist in our universe, should Earth be the only one where life or if you want living species exists in such abundance? The probability of this to be true is of course zero, but that is only my guess.
The universe must be full of life, sorry, I mean full of living species.
So, life is a miracle or not so much? Never mind, life is still the greatest precious wonder in the world and most of us humans forgot to feel it as such for the most part of our lives.