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.
It doesn't have a past tense as it's a noun.
The singular form of the demonstrative pronoun 'these' is this.
The singular form of feet is foot.
virtuoso
The singular form of "hypothysis" is "hypothesis."
The singular form is ombudsman.
it is already in its singular form.