A&G camera
 Acquisition and Guiding camera, see description of instrument subsystems
AESOPAustralian-European Southern Observatory Positioner, see description of instrument subsystems
AIPLeibniz-Institut für Astrophysik Potsdam, lead institute of the 4MOST Consortium
Consortium
The 4MOST Consortium is the group of institutes responsible for designing and building the 4MOST Facility, and for operating the instrument jointly with ESO
CRS
Cosmology Redshift Survey, one of the 4MOST Consortium Surveys, see description of Extragalactic Surveys
DXU
Data eXchange Unit, format for a given 4MOST data product, see description of data products
DMS
Data Management System, 4MOST system that will reduce, analyse, validate, and publish all data
eROSITA
extended ROentgen Survey with an Imaging Telescope Array, an X-ray imaging instrument to be launched in 2019, which will perform an all-sky survey
ESA
European Space Agency
ESO
European Southern Observatory, the organisation which owns and operates the VISTA telescope
Euclid
An optical/near-infrared space telescope to be launched by ESA in 2021
Fibre-hour
One hour of observing with one fibre
Field-of-View (FoV)
The size of the area on-sky that 4MOST can observe with one pointing
Figure-of-Merit (FoM) 
A quantity describing how much progress a 4MOST survey has made towards meeting its requirements during operations
Gaia
An ongoing ESA space mission designed to measure astrometry and photometry of more than one billion stars in the Milky Way. Gaia data will form the basis of the 4MOST Galactic Surveys' input catalogues.
GTO
Guaranteed Time Observations, in exchange for building 4MOST, the Consortium will receive 70% of the time available on 4MOST over the course of the five years
HRS
High Resolution Spectrograph, see description of instrument subsystems
L0, L1, L2
Different types of data products, see description of data products
LoI 
Letters of Intent, expression of interest by a member of the ESO community to propose for a Public Survey using 4MOST, see this description of the selection process for Community Surveys
LRS
Low Resolution Spectrograph, of which 4MOST will have two, see description of instrument subsystems
LSST
Large Synoptic Survey Telescope, an 8.4-m telescope currently under construction, with full operations scheduled for 2022. LSST will image the entire available sky every few nights for 10 years, in order to provide time-domain science.