Habit is usually something a person has, but custom can often be used in that role too: It was his habit/custom to get up early. Only habit is used in this phrase: He is in the habit of getting up early. Custom can be used to refer to something national: It's a Finnish custom to go to the sauna.
New words, one handy idiom, and a 2-minute quiz — delivered to your inbox to keep your streak alive.