I keep seeing in threads, and on the news, this issue about abortion, and equating it to murder. To be murder, you have to extinguish a life. So first a life must begin.

Can someone, without using the word "God", give me a clear definition of what that means?

My personal definition, is when an unborn child can live on it's own (or be saved with life support). So a 2 month old embryo, is not a life.

How do you define it?

I'm going to assume you want a definition of human life, not life in general.

I believe human life starts when self awareness is formed. While it's hard to tell when that happens, it's easy to tell when it does NOT happen. For example, without a brain there can be no self awareness.

That's a good definition... probably better then mine.

I would say as a bare minimum you could start life when an entity an first move independantly. If we wanted to get extremely technical I would say when the brain develops the necessary parts to regulate required bodily functions.

Life begins when you are born.

Mrs. Nerg has the answer.

I would go with about the 7th week after conception. From then it is absolutely evident that the fetus/child reacts to stimulus and has all of the qualities to define 'life'.

When the baby and mother aren't connected anymorw

Are single celled creatures like Amoebas alive?
Do we consider parasites that can not survive without a host to be alive?

So, basically a sperm or unfertilized egg are (infact) Alive and so is a fertilized egg ...

When does it become unethical to kill a living creature, and when a living creature becomes a human being are two seperate questions; I think most people would agree that it is fairly unethical to kill a living creature that is not causing you any harm, and the killing of it does not produce any personal benefit, long before it becomes a human being though ...

This is pretty much my assessment, when the child can survive outside the womb.  That is when you can without reservation say that the child is "alive." 

I mean by a very technical definition, every egg and every sperm is alive, so I really don't see why people draw the line at conception.  So technically you are killing future babies using condoms or taking birth control!  The logic kind of defeats itself eventually.

The other strong case is for when brainwave activity begins (somewhere around the end of the first trimester).

Development begins at conception, but "life" doesn't begin until much later.  Technically, the cells were always living, so just saying that they are alive doesn't do the trick.