An intensifier is a word, usually an adverb (e.g., very, extremely, incredibly), that strengthens or weakens another word (usually the word on its right). Intensifier has no real meaning itself and can usually be removed from the sentence.
The main purpose of an intensifier is to tell us about the intensity of another word.
It's a really interesting story.
Everyone was extremely excited.
Intensifiers with strong adjectives
The film was absolutely awful.
The food smelled really disgusting.
Intensifiers with particular adjectives
Like: dangerously ill
But not: highly tasty
Intensifiers with comparatives and superlatives
The blue whale is easily the biggest animal in the world.
This car was by far the most expensive.
Adjectives as intensifiers
We can say:
He's a complete idiot.They were talking total nonsense.
but we should not say:
The idiot was complete.The nonsense they were talking was total.