Chinese Putonghua (Mandarin) has 22 initials, including 21 consonant initials and the zero initial. Among the 21 consonant initials, 18 are represented by single letters (b, p, m, f, d, t, n, l, g, k, h, j, q, x, r, z, c, s), while the other three are represented by digraphs: zh, ch, sh.
The letters 'y' and 'w' are not classified as consonant initials from a phonetic perspective; they are orthographic devices used to prevent ambiguity when syllables begin with 'i', 'u', or 'ü'. Phonetically, they function as semivowels (/j/ and /w/) and are usually treated as part of the zero initial.
However, for pedagogical convenience, some textbooks list 'y' and 'w' together with the consonant initials in their initial charts. This is a teaching simplification, not a phonetic reality.
Some of these initials are similar to English sounds, while others are not.