Does anyone know what a coefficient of order unity is? I'm reading a journal paper and it gives the formula
[tex]P_{KOZ} \simeq P_1 \left( {\frac{{m_0 + m_1 }}{{m_2 }}} \right)\left( {\frac{{a_2 }}{{a_1 }}} \right)^3 \left( {1 - e_2^2 } \right)^{3/2} [/tex]
and then it says

.

It's on page 6 of this paper : http://www.journals.uchicago.edu/ApJ/journal/issues/ApJ/v535n1/40691/406 [Broken] 91.web.pdf

It means they are being sloppy and not calculating constants that go out front. These will be mathematical constants, like combinations of pi, e, etc, and will be not too small or too large, ie, probably in the range 1/10 to 10. So you might say what they have there is an approximation, although you should keep in mind that there is a constant that they could multiply it by that would make it exact for all values of whatever variable the function varies over, and this is something that isn't true in general of approximations.