  The concept of degree of similarity ({\eta}) is proposed to quantitatively
describe the similarity of a parameter (e.g. the maximum amplitude Rmax) of a
solar cycle relative to a referenced one, and the prediction method of similar
cycles is further developed. For two parameters, the solar minimum (Rmin) and
rising rate ({\beta}a), which can be directly measured a few months after the
minimum, a synthesis degree of similarity ({\eta}s) is defined as the
weighted-average of the {\eta} values around Rmin and {\beta}a with the weights
given by the coefficients of determination of Rmax with Rmin and {\beta}a,
respectively. The monthly values of the whole referenced cycle can be predicted
by averaging the corresponding values in the most similar cycles with the
weights given by the {\eta}s values. Cycles 14 and 10 are found to be the two
most similar cycles of Cycle 24. As an application, Cycle 24 is predicted to
peak around January 2013{\pm}8 (months) with a size of about Rmax
=83.0{\pm}16.7 and to end around September 2019.
