Certain comparative adjectives borrowed from Latin have no positive or superlative degree forms. All of these adjectives end in –or. They are 12 in all. Five of them have already lost their comparative meaning and are now used as positive adjectives. These are: interior, exterior, ulterior, major and minor.

He is an interior designer.

I have no ulterior motive in this.

He sustained minor injuries.

The other seven – inferior, superior, prior, anterior, posterior, senior, junior – are still used as comparative adjectives. But unlike normal comparative adjectives, they are followed by to instead of than.

He is senior to me. (NOT He is senior than me.)

James is superior to Peter in intelligence.

His marriage was prior to his father’s death.

He is junior to all his colleagues.

Certain adjectives express qualities that cannot be compared. Examples are: square, round, perfect, eternal, universal, unique etc.

Nothing can be more or less square or round.

She wore a perfect diamond on her finger. (NOT He wore a very perfect diamond on her finger.)

This plot is square. (NOT This plot is too square.)

However, there are a few exceptions to this rule. We can, for example, say the most perfect in some cases.

This is the most perfect specimen I have seen.