What are some examples plural forms like volcanos and mangos variant spelling?

You're right to point out that "volcanos" and "mangos" are variant spellings, and not the preferred ones. Here are some examples of plural nouns with variant spellings:

Standard Plural:

* Volcanoes (not volcanos)

* Mangoes (not mangos)

* Cacti (not cactuses)

* Amoebas (not amoebae)

* Octopi (not octopuses)

* Silos (not siloses)

* Zeroes (or zeros)

* Mottoes (or mottos)

Variant Plural:

* Alumnus/Alumni (singular/plural)

* Fungus/Fungi (singular/plural)

* Syllabus/Syllabi (singular/plural)

* Genus/Genera (singular/plural)

* Datum/Data (singular/plural)

* Octopus/Octopuses (or octopi)

Important Notes:

* -us/-i endings: Many words ending in "-us" form their plural by changing to "-i." (e.g., cactus/cacti).

* -o endings: Words ending in "-o" typically add "-es" to form the plural. (e.g., mango/mangoes). However, some exceptions exist (e.g., solo/solos, photo/photos).

* -es endings: Words ending in "-es" can be tricky. Some form their plural by simply adding an "-s" (e.g., box/boxes), while others add "-es" (e.g., church/churches).

* -y endings: If the word ends in a consonant followed by "-y," change the "-y" to "-ies" (e.g., baby/babies). If the word ends in a vowel followed by "-y," simply add an "-s" (e.g., boy/boys).

Remember, language is always evolving, and usage can vary depending on regional dialects and individual preferences. However, the standard plural forms are generally considered more formal and widely accepted.