1. Hf

noun. a grey tetravalent metallic element that resembles zirconium chemically and is found in zirconium minerals; used in filaments for its ready emission of electrons.


  • atomic number 72
  • hafnium
  • metal

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2. HF

noun. 3 to 30 megahertz.


  • high frequency
  • electromagnetic spectrum

Example sentences of the word hf

1. Noun, singular or mass
The energy (E) of a photon is related to Planck's constant and the photon's frequency (f) by the equation E = hf.