"Ŝ", or "ŝ", is a consonant and letter in the Esperantoalphabet. Since each letter in Esperanto has a consistent sound, this letter is always pronounced the same; its sound is represented by [S] in SAMPA.
... the square[?]. To "complete the square" is to add a constant (i.e., in this case, a quantity that does not depend on x) to the expression to the left of "=", that will ...