Virtuoso is singular, the plural form is virtuosi.
The singular form of virtuosi (or virtuosos) is virtuoso.
virtuosos
A virtuoso is a person that is highly skilled in music or another artistic form. Which means that a piano virtuoso is a person that is highly skilled in playing the piano specifically.
virtuosas
Tap dancing.
The singular form of the demonstrative pronoun 'these' is this.
The singular form of "that" is "it."
It doesn't have a past tense as it's a noun.
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.