The prefix "i-" is commonly used to denote negation or absence in words like "invisible" and "impossible." However, there are several synonyms for this prefix that can convey the same meaning in different contexts. For instance, "a-" is often used to mean "without" or "not," as seen in words like "asexual" and "amoral." "Non-" is another prefix that can be used to negate a word's meaning, like in "nonexistent" or "nonverbal." Finally, "un-" is a common prefix that denotes the opposite of a word's usual meaning, as in "unhappy" or "uncommon." Understanding the nuanced differences between these prefixes can allow for more precise language use.