[W/K] :: H piece

  H \H\ ([=a]ch),
     the eighth letter of the English alphabet, is classed among
     the consonants, and is formed with the mouth organs in the
     same position as that of the succeeding vowel. It is used
     with certain consonants to form digraphs representing sounds
     which are not found in the alphabet, as sh, th, [th], as in
     shall, thing, [th]ine (for zh see [sect]274); also, to modify
     the sounds of some other letters, as when placed after c and
     p, with the former of which it represents a compound sound
     like that of tsh, as in charm (written also tch as in catch),
     with the latter, the sound of f, as in phase, phantom. In
     some words, mostly derived or introduced from foreign
     languages, h following c and g indicates that those
     consonants have the hard sound before e, i, and y, as in
     chemistry, chiromancy, chyle, Ghent, Ghibelline, etc.; in
     some others, ch has the sound of sh, as in chicane. See Guide
     to Pronunciation, [sect][sect] 153, 179, 181-3, 237-8.
     [1913 Webster]
  
     Note: The name (aitch) is from the French ache; its form is
           from the Latin, and this from the Greek H, which was
           used as the sign of the spiritus asper (rough
           breathing) before it came to represent the long vowel,
           Gr. [eta]. The Greek H is from Ph[oe]nician, the
           ultimate origin probably being Egyptian. Etymologically
           H is most closely related to c; as in E. horn, L.
           cornu, Gr. ke`ras; E. hele, v. t., conceal; E. hide, L.
           cutis, Gr. ky`tos; E. hundred, L. centum, Gr.
           "e-kat-on, Skr. [.c]ata.
           [1913 Webster]
  
     H piece (Mining), the part of a plunger pump which contains
        the valve.
        [1913 Webster]