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From the National Institute for Health

In biology, it is generally agreed that organisms that possess the following seven characteristics are animate or living beings and thus possess life: the ability to respire, grow, excrete, reproduce, metabolize, move, and be responsive to the environment

The article as a whole elaborates that even trying to pin down a single definiton of life is a bit of a fool's errand, much less trying to use such a definition to support arguments about when life starts or stops.

From the Stanford Encyclopedia of Philosophy (which actually is just re-quoting an entirely different article, one of many discussed within)

We propose to define living systems as those that are: (1) composed of bounded micro-environments in thermodynamic equilibrium with their surroundings; (2) capable of transforming energy to maintain their low-entropy states; and (3) able to replicate structurally distinct copies of themselves from an instructional code perpetuated indefinitely through time despite the demise of the individual carrier through which it is transmitted.

From a University of Minnesota Introduction to Biology course

All groups of living organisms share several key characteristics or functions: order, sensitivity or response to stimuli, reproduction, adaptation, growth and development, regulation, homeostasis, and energy processing. When viewed together, these characteristics serve to define life.

In short, there really isn't any unified definition of life. Comparing different definitions, there's common themes that emerge, but nothing that supports saying conception is when it starts. If you're going to use that definition, you can't support it by saying that "science" defines it that way.