H

UK: 'H', 'h': /ˈeɪtʃ/ US: 'H', 'h': /eɪtʃ/ ,'H', 'h': (āch)

Collins Concise English Dictionary © HarperCollins Publishers::

H symbol

1. hydrogen
2. magnetic field strength
3. henry or henries
4. (on Brit pencils, signifying degree of hardness of lead) hard
   Compare B9

WordReference Random House Learner's Dictionary of American English © 2025

H, h /eɪtʃ/   n. [countable] , pl. Hs or H's, hs or h's. 

1. Linguistics the eighth letter of the English alphabet, a consonant.

H,  an abbreviation of:

1. hard.
2. Biochemistry, Slang Terms [Slang.] heroin.
3. high.

h,  an abbreviation of:

1. hard.
2. hardness.

h. or H., an abbreviation of:

1. hard.
2. hardness.
3. height.
4. high.
5. hour.

WordReference Random House Unabridged Dictionary of American English © 2025

H, h  (āch), n., pl. H's or Hs, h's or hs. 

1. the eighth letter of the English alphabet, a consonant.
2. any spoken sound represented by the letter H or h, as in hot or behave.
3. something having the shape of anH.
4. a written or printed representation of the letter H or h.
5. a device, as a printer's type, for reproducing the letter H or
   h.

H, 

1. hard.
2. Grammar head.
3. Chemistry, Electricity [Elect.] henry.
4. Biochemistry, Slang Terms [Slang.] heroin.
5. high.

H,  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.]
   • enthalpy.
   • horizontal component of the earth's magnetic field.
   • See magnetic intensity. 
6. Music and Dance the letter used in German to indicate the tone B.

H¹ ,[Symbol, Chem.]

1. Chemistry protium.

Also, ¹ H, H^a
H² ,[Symbol, Chem.]

1. Chemistry deuterium.

Also, ² H, H^b
H³ ,[Symbol, Chem.]

1. Chemistry tritium.

Also, ³ H, H^c
h, 

1. hard.

h, [Symbol, Physics.]

1. See Planck's constant. 

H., 

1. Drugs (in prescriptions) an hour.

• Latin hōra

h., 

1. harbor.
2. hard.
3. hardness.
4. heavy sea.
5. height.
6. hence.
7. high.
8. Sport [Baseball.] hit;
   hits.
9. horns.
10. hour;
    hours.
11. hundred.
12. husband.
Also, H. 

Collins Concise English Dictionary © HarperCollins Publishers::

h, H / eɪtʃ/ noun (h's, H's, Hs)

1. the eighth letter and sixth consonant of the modern English alphabet
2. a speech sound represented by this letter, in English usually a voiceless glottal fricative, as in hat
3. something shaped like an H
4. (in combination): an H-beam

h symbol

1. Planck constant
2. hecto-

Collins Concise English Dictionary © HarperCollins Publishers::

h., H. abbreviation

1. harbour
2. height
3. hour
4. husband