For speed we use a lot of abbreviations and acronyms. Here's a list of some of the more commonly used ones, please feel free to add your own if I've missed something important!
LFS- Local fish shop Amm- Ammonia NO2- NitrIte NO3- NitrAte CO2- Carbon dioxide pH- Potential of hydrogen. A scale to measure the acidity/alkalinity of water GH- General hardness. The concentration of dissolved magnesium and calcium in water KH- Carbonate hardness. The buffering capacity of water, ie stability of pH. SG- Specific gravity. The salinity of water. Only applies to brackish and marine set-ups. RO- Reverse osmosis. MTS- Malaysian trumpet snails DCF- Dwarf clawed frog WCMM- White cloud mountain minnows NTD- Neon tetra disease KHV- Koi herpes virus UGF- Under gravel filter PFK- Practical Fishkeeping (magazine)