durk, Can I say a two hours' work? "Work" is considered an activity. Articles are not used before activities like work, breakfast, school, etc. Example: I have work to do today...............not- I have a work to do today. I have school today......................not - I have a school today. I have two hours' work ahead of me.........correct without the article a two-hour drive You can say this. "Two-hour" is a compound adjective modifying drive. a two hours drive This is not correct. The drive belongs to the two hours. It is a drive of two hours.The apostrophe s is required after the plural noun hours. Many people write it this way. Do a search on google and you will see it, but still it is not considered grammatically correct. two hours' drive This is correct. You can use it with or without the article. Example: It is a two hour's drive from Detroit to Ann Arbor. It's two hours' drive from Kalamazoo to Lansing. All three of them are singular.

Actually the first two are both singular, since you are talking about the drive. Two hours' drive is a kind of possessive, think of the full sentence as "two hours worth of driving". 'Two hour drive' must be preceded by 'a' or 'the'. In this phrase the 'two-hour' part serves as an adjective, describing the drive. 'Two hours drive' sounds strange, and I probably would never use it. If it makes any sense, you could say this is the plural, and the 'drive' part is a verb. Eg. "I arrive home at 7pm, but I don't see my beloved wife until 9. The two hours drive me insane."