What differences are there between using 'at' and 'of' as prepositions before 'legal age' and other age-related noun phrases? I have encounter both constructions, though 'of' pops up more frequently in formal contexts. Why is that the case? Another pattern I noticed is that 'of' always immediately follows a noun, whilst 'at' enjoys greater flexibility. Bit what about the example below? Which one is the better fit and why?
- He is now [at (the) legal/of legal] age to go off to war.
Best Answer
The expression "of age" or, archaically, "of full age", means that an individual has reached the minimum age required. The person may be well over the minimum age. In your example, if the age to go to war is 18, then a 40-year old will be of age, just as much as an 18-year old.
The expression "at the age" is usually more specific. It would refer to an individual who has recently reached the minimum age required. Again in the example, an 18-year old would be described as being at the age while a 40-year old would not.