The plural form of the noun phenomenon is phenomena.The plural possessive form is phenomena's.Example: These phenomena's occurrences are very rare.
The plural of calculus is generally "calculi." The word "calculuses" is also a plural, but very rare.
ALGAE is the plural form, commonly used in place of the singular ALGA because references to a single organism are rare.
Mississippi is singular. Since there is only one state and one river by that name, it would be rare to have need of a plural form.
Some plural words that end in "f" include wolves, dwarves, and cliffs.
That is the correct spelling of the plural noun "pandas" (type of rare bear).
The plural of Nike (shoe) would be Nikes. Except in rare cases, apostrophes are not used to form plural nouns. The form Nike's would mean something about Nike.
Both the singular and plural future tense are "will jump." "Shall jump" is another option, although this is relatively rare in American English in the sense of a true future tense.
Domesticated pigs are kept in a sty (or stye (very rare)), the plural of sty is (according to OED, Chambers and Merriam-Webster) sties or alternatively (according to Chambers and Merriam-Webster) styes.
3. This is a rare word in English which uses a 2 plural morphemes. 1.Child- 2. -r- 3. -en -en is a rare (but not completely uncommon) plural morpheme. We see it in words like oxen. The -r- suffix was also used in middle English but only survives in this word, unless I am mistaken.
(The term is more often used as a plural.)The lack of governmental response in the crisis was a rare circumstance of non-intervention.
Yes, adding an apostrophe to the end of the plural noun knives forms the plural possessive noun knives'.Example: the knives' prices = the prices of the knives