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Sun-kissed mountains, ten-dollar bills, eleven-year-old daughter . . . What do these have in common?

They are Hyphenated Compound Adjectives.

Each of the phrases in the title of this blog post have compound adjectives (ten-dollar) that describe their nouns (bills).

A hyphen is needed between two words that function together as an adjective before the noun they describe.

Example: The sun-kissed mountains look beautiful this morning.

The words "sun" and "kissed" work together to describe the mountains being lit up by the sun.

Example: My 11-year-old daughter has a birthday coming up.

When an age comes before the person whose age it is, hyphens are needed as seen above because their age is an adjective describing them in some way.

As opposed to: My daughter is almost 12 years old.

In this sentence above, my daughter's age comes at the end of the sentence. Her age isn't being used as an adjective before the subject (daughter) in the sentence, so no hyphens are needed.