Hyphenated ages
Has hyphenation of ages become the standard in all grammatical contexts?
When I was in school (60's and 70's), here is how ages were presented:
Rover is a 12-year-old dog.
Rover is 12 years old.
In other words, if the age functioned as an adjective, it was hyphenated; as a copulative predicate, it was not.
Now I seldom see, even in formal publications, the non-hyphenated form. Instead, it's:
Rover is a 12-year-old dog.
Rover is 12-years-old.
Oddly, I only rarely see this form extended to other measurements, like height or time.
Rover is a 30-centimeter-tall dog.
Rover is 30 centimeters tall.
RARELY: Rover is 30-centimeters-tall.
It was a 100-year war.
The war lasted 100 years.
RARELY: The war lasted 100-years.
Anyone have a copy of Chicago Manual of Style or other authoritative source handy?
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