Addendum is the singular form; the plural form is addenda, although there is some acceptance for addendums as the plural.
The plural form is addenda.
analysis itself is a singular form
The noun genius is the singular form, the plural form is geniuses.
The noun form 'cut' is singular; the plural form is 'cuts'.
The singular possessive form of criterion is criterion's
The plural form is addenda.
The singular form of the demonstrative pronoun 'these' is this.
The singular form of "that" is "it."
The singular form is cuff.
it is already in its singular form.
"Stratum" is the singular form of stratum. The plural form is "strata".
PS.....Post script adendum
The form hypothesis is the singular form. The plural form is hypotheses.
A singular form of dice is a die
The singular form of feet is foot.
The singular form of Oases is, Oasis.
Phenomenon is the singular form of phenomena.