One of the charming features of Chinese is reduplication of certain words and characters, including adjectives in Chinese grammar!

Basic patterns

One way to intensify adjectives is to reduplicate them. This creates a sense of "really" or "very", and makes the descriptive power of the adjective stronger.

In most Chinese textbooks and grammar books, this is known as the "AA" pattern. For example:

Nǐ de liǎn hónɡ hónɡ de 。
你的 脸 红红的。
Your face is very red.

If the adjective has more than one character, then you should repeat each character individually. This is known as the "AABB" pattern. Examples:

ɡāo ɡāo xìnɡ xìnɡ
高高兴兴
very happy

Note: The "AABB" pattern for reduplication of two-syllable adjectives contrasts with the "ABAB" pattern for reduplication of two-syllable verbs.