How to use of term "both"?

Question

In which of the sentences would the "both" be right, grammatically?

a) "Such conditions are both dominant during the..."

b) "Such conditions are dominant both during the..."

Answer 1

It depends on the context.

a) "Such conditions are both dominant during the..."

If there are exactly two conditions that are dominant during a specified period.

or

b) "Such conditions are dominant both during the..."

If there are some number of conditions dominant during exactly two seperate periods.

So both can be correct, depending on what comes after the "..."

---

For example:

Red and blue are both dominant colours of national flags.

here we see exactly two things (red and blue) that are dominant.

or

Red and blue are dominant, both in national flags, and in political party colours.

here we see red and blue dominant in exactly two things.

[EDIT: as user Ruakh has said the following is not correct, a comma is not necessary.]

One important thing to note is that the second example "dominant both" should have a comma after "dominant". Since it does not, in the absense of context I would say example (a) is more likely to be correct.

Answer 2

Well...both of them! With slightly different meanings.

The word both is used to indicate the beginning of a list of two items; the list is normally going to be separated by and.

The first sentence would make sense if the conditions are dominant in one situation, and irrelevant in a second situation.

Such conditions are both dominant during the first phase of the test, and sidelined during the third phase.

The second example would make sense if you're going to list two situations where the conditions are dominant.

Such conditions are dominant both during the first phase of the test and during the third phase.

Both indicates that whatever has come before it is applicable to two items that follow it. So the first example could be written thus:

Such conditions are dominant during the first phase of the test. Such conditions are sidelined during the third phase of the test.

The second example could be written as:

Such conditions are dominant during the first phase of the test. Such conditions are dominant during the third phase of the test.