PSD: The particle-size distribution of a powder, or granular material, or particles dispersed in fluid, is a list of values or a mathematical function that defines the relative amount, typically by mass, of particles present according to size. Significant energy is usually required to disintegrate soil, etc. particles into the PSD that is then called a grain size distribution.

PM: Particulate matter, also known as particle pollution, is a complex mixture of extremely small particles and liquid droplets that get into the air. Once inhaled, these particles can affect the heart and lungs and cause serious health effects.

SN: smoke numbers

Soot particles: Soot is a mass of impure carbon particles resulting from the incomplete combustion of hydrocarbons. It is more properly restricted to the product of the gas-phase combustion process

NOx: nitrogen oxide

CO2: carbon dioxide

HO: hydroxide 

TRL: Technology readiness levels are a method of estimating technology maturity of Critical Technology Elements (CTE) of a program during the acquisition process. They are determined during a Technology Readiness Assessment (TRA) that examines program concepts, technology requirements, and demonstrated technology capabilities. TRL are based on a scale from 1 to 9 with 9 being the most mature technology.

ACARE: The Advisory Council for Aeronautics Research in Europe (ACARE) is a European advisory body that aims to improve the competitiveness and sustainability of the European Union in the field of aeronautics. It is a public-private partnership between the Directorate-General for Transport and Energy of the European Commission and industry leaders.

ICAO: The International Civil Aviation Organization is a specialized agency of the United Nations. It codifies the principles and techniques of international air navigation and fosters the planning and development of international air transport to ensure safe and orderly growth.