Also known as the Pearson product-moment correlation coefficient, the correlation coefficient (r) measures the linear relationship between two variables, with a value range of -1 to 1. A value close to 1 indicates there is a strong positive linear correlation between two variables; that is, when one variable increases so does the other.
A short definition. Delta H of a reaction is the enthalpy of reaction. H of products minus H of reactants. Each compound has a delta H of formation (dHf). The heats of formation for each substance in a reaction can be added together to compute the energy change for a reaction.
delta. Fourth letter in Greek alphabet, the word Delta means a change in quantity (more rarely quality). Take the value for the first day of each week and subtract it from the value at the next to obtain the weekly deltas. Rates have gone up, but I converted to fixed, so my Delta hasn't been too bad.