[Atome]

I don't understand the differences between 'differential' and 'different' as adjectives in the quotations below. English isn't my first language. Why do these books use 'differential' as an adjective? Why not just write 'different'?

1. Handbook of the Biology of Aging edited by Edward J. Masoro, Steven N. Austad. p 480.

2. The Cambridge Companion to the Philosophy of Biology edited by David L. Hull, Michael Ruse. p 46.

3. p 78.

4. Dictionary of Plant Genetics and Molecular Biology by Gurbachan Miglani. Anyone know the page #?

[Babcock_Hall]

1a : of, relating to, or constituting a difference : DISTINGUISHING
differential characteristics
b : making a distinction between individuals or classes
differential tax rates
c : based on or resulting from a differential
d : functioning or proceeding differently or at a different rate
differential melting

(From Merriam Webster's dictionary)

I would say that definition b is most relevant here, but I am far from certain.

[Corribus]

Actually I think definition d may be most relevant. Differential is a mathematical (calculus) term, literally meaning the derivative of some variable (position) with time, which is formally a rate. So "differential deaths" may be implying a difference in death rate between two time points. I.e., how much an observed variable changes over the course of a finite time period.

Example: if you make a point observation of two things, that's observing a difference (this bread is more moldy than that bread). If you make an observation of how two things change over time (this loaf of bread turned more moldy between yesterday and today than that loaf of bread), that's observing a differential.