What is the plural form of “cactus”?

The plural form of "cactus" is "cacti." This follows the Latin-based rule for pluralization where nouns that end in "-us" typically change to "-i" in their plural form. Cactus, being derived from Latin, adheres to this convention. Therefore, "cacti" is the correct way to refer to multiple cactuses in a manner consistent with the traditional language rules from which the term originates.

While "cactuses" is also a commonly accepted English form of the plural, it is not the classical formation. The other choices, "cactae" and "cactusese," do not represent standard English pluralizations and are not recognized as correct in either traditional or modern usage. Therefore, "cacti" remains the most suitable and accurate plural form, especially in a formal or botanical context.