'three'.

i was born in 1993.
i was the 3rd kid in the family.
i'm in 2/3.
my register number is 23.
i wish i was 3 years old right now.
i've been painting for 3 years.
i ate 3 oysters just now.
i'm 13 today.
it's been 3 years already.

the square-root of 9, the number of sentences above is 3.