The noun form, Chinese, is an uncountable noun; a word for one person from China or the entire population of China. Example:
My father is Chinese, from Wuhan on the Yangtze River.
A group of Chinese will be meeting with the committee today.
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."
The singular form of diagnoses is diagnosis.