oper - oxyg
- operating analysis
- operating cycle
- operating level
- operating standards
- operation conditions
- operational area
- operational cleanliness level
- operational hydrology
- operational hydrology program
- operational planning
- operational pollution
- operational stability
- operational waste
- OPI
- optical depth
- optical monitoring
- optical particle counter
- optical pollution
- optical probe monitoring
- optical rain gage
- optical window
- optical-acoustic
- optical-acoustic gas analyzer
- optically active gas
- optically active pollutants
- optically clear
- optimal density
- optimisation model
- optimization criteria
- optimization model
- optimization of environment
- optimization of resources management
- optimum
- optimum land-use and cropping plan
- optimum moisture
- optimum population
- option price
- option value
- options for facilitating access by and transfer to developing countries of environmentally sound technologies on favourable terms
- OPTS