Definitions of habit:

• noun:   a pattern of behavior acquired through frequent repetition

  Example: "She had a habit twirling the ends of her hair"

• noun:   (religion) a distinctive attire (as the costume of a religious order)
• noun:   an established custom

  Example: "It was their habit to dine at 7 every evening"

• noun:   excessive use of drugs
• verb:   put a habit on