When reading about radioactive decay, I see two types of decay constants: λ and "k". From what I have interpreted, k = ln (.5) / half-life whereas λ = ln (2) / half-life. Have I defined these correctly? If this is so, the difference between the two is slight. When putting these into equations, we see: Nt = N0*ekt Nt = N0*e-λt The only difference seems to be that when using lambda, you have to remember to put the negative sign in the exponent. It just seems confusing to me that some authors use λ whereas others use "k".