It is known that two consecutive coefficients of a ternary cyclotomic polynomial ${\Phi }_{pqr}\left(x\right)={\sum }_k{a}_{pqr}\left(k\right)x^k$ differ by at most one. We characterize all k such that $|a_{pqr}\left(k\right)-a_{pqr}(k-1)|=1$. We use this to prove that the number of nonzero coefficients of the nth ternary cyclotomic polynomial is greater than $n^{1/3}$.