'ten year old' vs 'ten years old' Generally, when units of me | Grammar Guy
"ten year old" vs "ten years old"
Generally, when units of measure are used as adjectives (prenomial), or as part of a compound noun, they are singular. When expressed as simple nouns, they are plural.
- A ten-year-old girl is sitting on the couch. (prenomial) - The girl sitting on the couch is ten years old. - The girl sitting on the couch is a ten-year-old. (compound)
- The bureau is 3 meters long. - This is a 3-meter-long bureau. (prenominal)
- The period is 2 weeks. - This is a 2-week period. (prenominal)
- The bill was 3 dollars. - This is a 3-dollar bill. (prenominal)
