The word "ATER" can be spelled as A-T-E-R. In IPA phonetic transcription, it would be represented as /ˈeɪ.tər/. The first sound is the long A sound, followed by the T sound and the short E sound. The final R sound is pronounced as a schwa, which is a neutral vowel sound. Proper spelling is important for clear communication and understanding, especially in written communication where there is no context to provide meaning.
Pure black; as a prefix, spelt atro.
Etymological and pronouncing dictionary of the English language. By Stormonth, James, Phelp, P. H. Published 1874.