The word buffalo.
Which word has three different acceptable ways to form the plural
Yes
The acceptable plural form is tomatoes.
R's is the plural form of r, but Rs is acceptable although not the preferred form.
Pair or pairs is the plural form of pair. Both are acceptable.
Appendixes or appendices is the plural of appendix. Both are acceptable
Formulas or formulae is the plural of formula. Both are acceptable
The plural form of the noun is focuses or foci. Either is acceptable.
Musea is an acceptable form for the plural but museums is used more often.
The plural form for the noun thief is thieves.
Manifestos or manifestoes. Both are acceptable.
The plural forms thesauruses and thesauri are both acceptable forms of the word thesaurus.