The 'o' in 'omicron' is short, like in 'off', not long as in 'mode'. Pronounce it 'AH-muh-krahn', not 'oh-MEE-kron'.
Pro Tip 2/3
Not Numeric
'Omicron' represents a letter, not a number, unlike Roman numerals. 'Omicron' is a letter, just like 'A' in the English alphabet.
Pro Tip 3/3
Greek Origin
Knowing 'omicron' is Greek helps when encountering other Greek terms in English. After learning 'omicron', Greek words like 'epsilon' or 'beta' will feel familiar.