@wikipedia
Synonym: Standard Conditions = STP = s.c. = SPE STP
A specific combination of temperature and pressure:
This definition follows SPE Standards and may not match the same terms in other industries.
The most popular alternative specification is provided by IUPAC which differs from SPE STP in temperature reference: IUPAC Reference Temperature = 273.15 K = 0 °C = 32 °F = 491.67 °R.
It should not be confused with Normal Conditions (NTP) which is a different specification.
See also
Natural Science / Engineering / Measurement / Unit