Select the most appropriate one-word substitution for the given group of words.

"A person's unusual behaviour or habit "

Idiosyncrasy

The most appropriate one-word substitution for the given group of words is idiosyncrasy.

• Intelligent means having or showing a high degree of intelligence.
• Dumb means lacking in intelligence or understanding.
• Psycho means having a mental disorder.
• Idiosyncrasy means a peculiarity or distinctive trait of a person or thing.