What's the difference between pian, tang, wan, gao, and shui?

Chinese medicine comes in many different formats. Here's what certain common words mean:

PIAN (片 - Piàn)
Tablet (modern looking pill)

WAN (丸 - Wán)
Pill (old-style or handmade pill, or black teapill)

TANG (湯 - Tāng)
Water Decoction (boiled whole herbs)

SAN (散 - Sàn)
Powder (milled or granulated)

SHUI (水 - Shuǐ)
Tincture (extract with alcohol or other solvent)

GAO (膏 - Gāo)
Paste (topical unguent or plaster)

JIAO NANG (胶囊 - Jiāonáng)
Capsule

DAN (丹 - Dān)
Pellet or Powder