What is the difference between "twenty-four-hour shift" and twenty-four hour shift"? [closed]

Solution 1:

Compound Numbers that are below one hundred and made up of two words require hyphenation.

Compound adjectives used before a noun are hyphenated as well, requiring "24" and "hour" to be hyphenated in "24-hour shift".

So only example 3, "I am doing a twenty-four-hour shift tonight" is correctly hyphenated. When read aloud, of course, all three orthographies sound the same.

Note that the first example appears to be badly hyphenated rather than referring to twenty shifts of four hours each. Presence of the indefinite article "a" and use of "shift" in the singular indicate only one shift is being talked about.

Solution 2:

A better example of the hyphens altering the meaning would be if you were to isolate the noun phrases in question:

1. Twenty four-hour shifts
2. Twenty-four hour shifts
3. Twenty-four-hour shifts

In these examples each would mean something different:

1. 20 x 4-hour shifts
2. 24 x 1-hour shifts
3. Shifts that last 24 hours