Difference between 'required primarily' and 'primarily required'

Question

I was reading a scientific article and encountered the sentence 'Lack of A prevents the activation of B, which is primarily required for digestion, and later for the absorption of....', where A and B are some proteins.

What confused me was the usage 'primarily required'. I felt that 'required primarily' would be a better choice. I actually did not understand why I felt that. So I tried to find the difference between the two usages.

I did find some articles that used both expressions, but none that explained the difference, if there are any. Ngrams shows that both are used at similar rates even though 'primarily required' has been used slightly more in the recent years.

What I want to know is, do the two expressions convey different meanings? If so, what is it? Can someone please help me?

Answer 1

Lack of A prevents the activation of B, which is primarily required for digestion

B is required for digestion but can do other things. We don't care about the other things B can do because we only care about what's required for digestion at the moment.

Lack of A prevents the activation of B, which is required primarily for digestion

B is required for digestion but can do other things. Other things matter but will be secondary in importance.

Answer 2

Your question is about the position of an adverb that modifies an adjective, whether it should be placed before or after the adjective it modifies.

This source explains:

adverb-adjective

When adverbs modify adjectives, they are placed immediately before them:

We had some really interesting news last night. John's been offered a job in Australia. He's absolutely delighted.

I bought an incredibly expensive dress last week which fits me perfectly. But John says I shouldn't wear it. He says it's too tight.

An exception to this rule is enough which is placed after the adjective or adverb that it modifies:

I got up quite early but not early enough to eat a good breakfast.

So, according to these rules, in your case the adverb would have to be placed as follows:

Lack of A prevents the activation of B, which is primarily required for digestion, and...

However, sometimes, there are exceptions to the general rule, therefore these rules should be regarded as a basic guide. So, my point is that there is an exception in your particular case, and both versions are grammatical and can be employed depending on the emphasis that is meant.

Answer 3

The source of confusion comes from the meaning of the combination of words within the overall context, rather than their order or position. The fact that B is simply REQUIRED for digestion seems to be the primary point, not whether B is PRIMARILY required for digestion.