a/the

English as a Second Language English Vocabulary, Grammar and Idioms
1

“What we need is a/the most perfect plan?”
Which article is best suited here? Why?

2

Both can be used. What we need is a perfect plan. What we need is the perfect plan. I would use the latter because it implies that there is only one plan. It seems stronger, less ambiguous to me. Anyone else?

3

I would call ‘perfect’ an ungradable adjective. You can’t be more or less perfect; you are either perfect or imperfect.

What we need is the perfect plan. Presumably for any single project, only one plan is perfect; the rest are imperfect.

4

Mister Micawber,

  1. Most of the time, we have a perfect relationship.
  2. Most of the time, we have a good relationship.
    I believe both sentences are OK.
    Which one is most adopted by natives?
5

As you say, both are OK. They carry different meanings: different qualities of relationship. So I would use the one I meant.