DIH or dih may refer to:
Dihydrotestosterone (DHT), or 5α-dihydrotestosterone (5α-DHT), also known as 5α-androstan-17β-ol-3-one, is an endogenous androgen sex steroid and hormone.
The dihydrogen monoxide hoax involves calling water by the unfamiliar chemical name "dihydrogen monoxide" (DHMO), and listing some of water's effects in an alarming manner (for example: it accelerates corrosion or can cause suffocation).
Dihydrocodeine is a semi-synthetic opioid analgesic prescribed for pain or severe dyspnea, or as an antitussive, either alone or compounded with paracetamol (as in co-dydramol) or aspirin.
Dihang-Dibang or Dehang-Debang is a biosphere reserve constituted in 1998. It is in the Indian state of Arunachal Pradesh.
Dihedral angle is the upward angle from horizontal of the wings or tailplane of a fixed-wing aircraft.
Dihydrofolate reductase, or DHFR, is an enzyme that reduces dihydrofolic acid to tetrahydrofolic acid, using NADPH as electron donor, which can be converted to the kinds of tetrahydrofolate cofactors used in 1-carbon transfer chemistry.
In mathematics, a dihedral group is the group of symmetries of a regular polygon, which includes rotations and reflections.
Dihydroergotamine (DHE) is an ergot alkaloid used to treat migraines. It is a derivative of ergotamine.
A dihedral angle is the angle between two intersecting planes. In chemistry it is the angle between planes through two sets of three atoms, having two atoms in common.