HJ

HJ may refer to:

Mathematics and science

• HJ, Hall–Janko group, a mathematical group
• HJ, Heterojunction, the interface between two layers of dissimilar crystalline semiconductors

Other

• HJ, Hilal-i-Jurat, the second highest military award of Pakistan
• HJ, Hitler-Jugend, the German name for the Hitler Youth
• HJ, a Latin abbreviation for hic jacet ('Here lies'), commonly used on gravestones. See List of Latin phrases (H)
• Hj. (Hajji), an Islamic honorific
• 'The HJ', Halliwell Jones Stadium, a stadium in Warrington, England
• HJ, U.S. code word for a cryptographic key change (see Cryptoperiod)
• The IATA airline designator for Tasman Cargo Airlines
• Holden HJ, An Australian full sized car produced between 1974 & 1976
• ⟨hj⟩, a two-letter combination used in some languages
  • hj-reduction, a process affecting the pronunciation of English words like human in some dialects