The singular form of 'parentheses' is 'parenthesis'.
It depends on what your doing, the most common use of parenthases is when you put a number next to the one in parenthases that means you multiply the numbers 4(5)=20
The singular form of the demonstrative pronoun 'these' is this.
The singular form of "that" is "it."
it is already in its singular form.
The singular form is cuff.
"Stratum" is the singular form of stratum. The plural form is "strata".
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.
The singular form of chromosomes is a chromatid.
"Wash" is the singular form of "wash."