1

Should it be 30 day free trial or 30 days free trial?

I believe it should be 30 day free trial but I can't find the grammar rule to back this up. I am trying to explain it to someone who is not a native English speaker.

Renae Lider
  • 365

1 Answers1

1

The phrase is commonly used in its singular form:

You are eligible for a 30-day trial

Another well known example would be the usage "30 year old man" rather than "30 years old man"

This pattern goes all the way back to Old English (alias Anglo-Saxon). It's the same reason many of us say that someone is "5 foot 2" rather than "5 feet 2".

The source of the idiom is the old genitive plural, which did not end in -s, and did not contain a high front vowel to trigger umlaut("foot" vs "feet"). When the ending was lost because of regular phonetic developments, the pattern remained the same, and it now seemed that the singular rather than the plural was in use.

Renae Lider
  • 365
  • Nobody ever spoke “Anglo-Saxon”. The language they spoke is one they themselves called English (although not with that spelling). It must be learned as a foreign language by modern speakers of English, because the tongue of Beowulf that was spoken by “English” kings like Alfred the Great (Ælfrǣd, Elf-rede) is at too far remove from the modern language of that name for it to be understood without training. This is due to the historical events starting from 1066 onwards that brought a huge influx of vocabulary from Romance and elsewhere. – tchrist Sep 24 '14 at 13:21