H

1. hard.

2. Gram. head.

3. Elect. henry.

4. Slang. heroin.

5. high.

Symbol.

1. the eighth in order or in a series.

2. (sometimes l.c.) the medieval Roman numeral for 200. Cf. Roman numerals.

3. Chem. hydrogen.

4. Biochem. histidine.

5. Physics.

a. enthalpy.

b. horizontal component of the earth's magnetic field.

c. See magnetic intensity.

6. Music. the letter used in German to indicate the tone B.

H¹

Symbol, Chem.

protium.

Also, ¹H, H^a.

H²

Symbol, Chem.

deuterium.

Also, ²H, H^b.

H³

Symbol, Chem.

tritium.

Also, ³H, H^c.

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