In alphabetical order:

baby ginger See green ginger.

Chinese ginger See fingerroot.

Chinese key See fingerroot.

fingerroot = Chinese ginger = Chinese key = ka chai = kra chai = krachai Latin name: Kaempferia galanga
Notes: This ginger relative is popular in Thailand. It resembles long fingers jutting from a hand.
Substitutes: lesser galangal OR galangal (MUCH sharper flavor) OR ginger.

fresh ginger See ginger root.

gari pickled ginger
see How To Make Your Own Gari (Pickled Ginger For Sushi) galanga (ginger) See galangal (just below).

galangal = galanga (ginger) = greater galangal = (greater) galingale = (greater) galangale = Java root = Java galangal = kha = khaa = languas = lengkuas = laos (root or ginger) = Thai ginger = Siamese ginger Latin name: Alpinia galanga
Notes: Look for this in Asian markets. It's sold fresh, frozen, dried, or powdered. Use the dried or powdered versions only in a pinch.
Substitutes: ginger (not as pungent as galangal)

galangale See galangal (just above).

galingale See galangal.

geung See ginger root.

ginger (root) = gingerroot = fresh ginger = geung = khing = shoga
Equivalents: 1/4 cup, sliced = 1 ounce
Notes: If a recipe for a baked good calls for ginger, it's probably referring to ground ginger. Don't substitute ground ginger for fresh ginger; it's not nearly as pungent. Dried whole ginger is a better substitute for fresh, as is the minced or puréed ginger that's sold in jars.
Equivalents: 1 tablespoon fresh = ¼ teaspoon ground
Substitutes: green ginger (not as flavorful) OR galangal (More pungent than ginger, but works well in many spicy Asian dishes.) OR crystallized ginger (Substitute 1/4 cup minced crystallized ginger for every tablespoon of minced fresh ginger called for in recipe. Rinse off the sugar before using.)

gingerroot See ginger root.

green ginger = spring ginger = new ginger = young ginger = stem ginger = pink ginger = baby ginger
Notes: These pink-tipped young pieces of ginger are milder and usually don't need to be peeled. They're easy to find in Asian markets.
Substitutes: ginger (more pungent).

greater galangal See galangal.

greater galangale See galangal.

Indian ginger Isn't. It's turmeric. Although it is a rhizome.

Java root See galangal.

Java galangal See galangal.

ka chai See fingerroot.

kencur root See lesser galangal.

kentjur root See lesser galangal.

kha See galangal.

khaa See galangal.

khing See ginger root.

kra chai = krachai See fingerroot.

languas See galangal.

laos (root or ginger) See galangal.

lengkuas See galangal.

lesser galangal = lesser galangale = kencur root = kentjur root = zedoary
Notes: This Indonesian rhizome looks a bit like ginger, only it's smaller and darker. It's hard to find, but look in Asian markets and you might get lucky. It's sold fresh, frozen, pickled, dried, or powdered. Used the dried or powdered versions only in a pinch. One teaspoon powdered = two teaspoons fresh minced.
Substitutes: fingerroot OR galangal (sharper flavor) OR ginger

lesser galangale See lesser galangal.

mango ginger Isn't. Again, it's turmeric.

new ginger See green ginger.

pink ginger See green ginger.

shoga See ginger root.

Siamese ginger See galangal.

spring ginger See green ginger.

stem ginger See green ginger.

turmeric = fresh turmeric = Indian ginger = yellow ginger = mango ginger
Pronunciation: TUR-muhr-ik
Shopping hints: Look for fresh roots in Southeast Asian markets. Ground turmeric is the powdered version.
Equivalents: 1 piece fresh turmeric = 1 teaspoon powdered turmeric.
Substitutes: ground turmeric OR saffron (which is much more expensive, and more flavourful) OR Steep annatto seeds in boiling water for 20 minutes, then discard the seeds.

Thai ginger See galangal.

yellow ginger See turmeric.

young ginger See green ginger.