Question

Sam's daugter is six-year old/six years old.​

Answer 1

The correct sentence will be:

Sam's daughter is six years old.

• In English language, the correct sentence structure, grammar and tense are important in order to frame a correct sentence.
• As six is not a single number i.e more than one, hence plural for of year will be used.
• If the age was expressed before the noun, as an adjective, then it would have been written as 'year' but as here the age is mentioned after the noun 'years' will be used.