aŭtoro

The aŭ is one syllable, a diphthong, so the word is AŬ-to-ro in three beats and not four. Meaning-wise, aŭtoro is tied to a particular work: you are the author of something. Verkisto is the trade, someone who writes for a living whether or not you have any given book of theirs in hand. The base form covers writers of either sex and aŭtorino is available when the distinction matters, though plain aŭtoro is the modern default. Aŭtoreco is authorship, the fact of having written the thing.