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Definition(s) of “H”

h |ā ch |

abbreviation

• (in measuring the height of horses) hand(s).

• [in combination ] (in units of measurement) hecto- : wine production reached 624,000 hl last year.

• horse.

• (esp. with reference to water) hot : nine rooms, all with h & c.

• hour(s) : breakfast at 0700 h.

symbol

• Physics Planck's constant.

H 1 |ā ch | (also h)

noun ( pl. Hs or H's |ˈā ch iz|)

1 the eighth letter of the alphabet.

• denoting the next after G in a set of items, categories, etc.

• ( h) Chess denoting the file on the right-hand edge of the board, as viewed from White's side.

2 ( H) a shape like that of a capital H.

3 ( H) Music (in the German system) the note B natural.

H 2

abbreviation

• hard (used in describing grades of pencil lead) : a 2H pencil.

• height (in giving the dimensions of an object).

• Physics henry(s).

• informal heroin.

symbol

• Chemistry enthalpy.

• the chemical element hydrogen.

• Physics magnetic field strength.

henry |ˈhenrē| (abbr.: H)

noun ( pl. henries or henrys ) Physics

the SI unit of inductance, equal to an electromotive force of one volt in a closed circuit with a uniform rate of change of current of one ampere per second.

ORIGIN late 19th cent.: named after Joseph Henry (1797–1878), the American physicist who discovered the phenomenon.

hydrogen |ˈhīdrəjən|

noun

a colorless, odorless, highly flammable gas, the chemical element of atomic number 1. (Symbol: H)

Hydrogen is the lightest of the chemical elements and has the simplest atomic structure, a single electron orbiting a nucleus consisting of a single proton. It is by far the commonest element in the universe, although not on the earth, where it occurs chiefly combined with oxygen as water.

DERIVATIVES

hydrogenous |hīˈdräjənəs| adjective

ORIGIN late 18th cent.: coined in French from Greek hudro- ‘water’ + -genēs (see -gen ).

enthalpy |ˈenˌθalpē; enˈθalpē|

noun Physics

a thermodynamic quantity equivalent to the total heat content of a system. It is equal to the internal energy of the system plus the product of pressure and volume. (Symbol: H)

• the change in this quantity associated with a particular chemical process.

ORIGIN 1920s: from Greek enthalpein ‘warm in,’ from en- ‘within’ + thalpein ‘to heat.’