posted by rfvv Monday, June 18, 2018 at 4:52pm

1. The flea market is open every 4th Saturday.
2. The flea market is open every four Saturdays.

3. He takes a shower every second day.
4. He takes a shower every two days.
...........
#3 and #4 are the same. What about #1 and #2? Are both the same as well?

PsyDAG Tuesday, June 19, 2018 at 2:14pm
2 is not as clear as 1.
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Thank you for your help.

1. The flea market is open every 4th Saturday.
2. The flea market is open every four Saturdays.
[#1 is correct, grammatical and commonly used. What about #2? Is #2 not grammatical? Or is #2 grammatical, but not commonly used?]

5. The conference is held every 4th year.
6. The conference is held every four years.
[They are both grammatical and no problem in using them, aren't they?]

All are g grammatical. Number two is, as PsyDAG said, not clear. We would not say it that way. Number one is much better. Five and six are both fine as they are and clearly mean the same thing.

In regards to the first question, the difference between "The flea market is open every 4th Saturday" (#1) and "The flea market is open every four Saturdays" (#2) is slight but important.

#1 is a more common and commonly used way of expressing that the flea market is open on the fourth Saturday of every month. This means that regardless of the month, the market will always be open on the fourth Saturday.

#2, on the other hand, could be interpreted in two ways. On one hand, it could mean that the market is open for four consecutive Saturdays, and then closed for the next set of four Saturdays. This would be a cyclical schedule where the market alternates between open and closed on successive sets of four Saturdays.

On the other hand, #2 could also simply mean that the market is open on any random four Saturdays throughout the year. There is no specific pattern or regularity. This interpretation relies heavily on the context and inference.

In regards to the second question, both #5 ("The conference is held every 4th year") and #6 ("The conference is held every four years") are grammatically correct and there is no problem in using them. They convey the same meaning in terms of the frequency of the conference, meaning that it is held once every four years.