A light-year is a unit of distance - the distance travelled by light in a year. Light travels 300,000 km in a second, so a light-year is about 9.5 x 1012 (9.5 million million) kilometers.
"Lightyear" is a noun. It is a unit of distance used to measure interstellar space.
lightyear
lightyear.
A lightyear is the distance that light can travel in one year.
a Lightyear, around 1013 kilometres.
Please note that a light-year is a distance. As far as I know, the square root of a distance is not something that makes sense physically - in other words, you can express it mathematically, but it's not a unit used in practice.
Buzz Lightyear
a mega lightyear
A lightyear is a much larger distance.
Lightyear Capital was created in 2002.
Lightyear Capital's population is 20.
Buzz Lightyear