Glossary
What is ATIS?
A recorded broadcast at a busier airport carrying the current weather, the runway in use and any field conditions, re-recorded as things change and labelled with a letter of the phonetic alphabet. Pilots listen to it before calling the controller and state the letter to show they have it.
Also called Automatic Terminal Information Service
That is the whole entry for now. The longer version, with the mechanics and worked examples, is still to be written. See autorotation for how those read once they exist.