cus·tom 
(kŭstəm)
(kŭstəm)n.
1.
a. A traditional practice or usual way of doing something followed by a social group or people.
b. The tradition or body of such practices: The respect that is by custom accorded to the king.
2.
a. A habitual practice of a person: my custom of reading a little before sleep. See Synonyms at habit.
b. Habitual manner or practice: I am not by custom a coffee drinker.
3. Law A common tradition or usage so long established that it has the force or validity of law.
4. Habitual patronage, as of a store: tried to obtain the custom of the wealthiest shoppers.
5. customs
a. Duties or taxes imposed on imported and, less commonly, exported goods.
b. (used with a sing. verb) The governmental agency authorized to collect these duties.
c. (used with a sing. verb) The place where goods and baggage entering a country are inspected by this agency: go through customs.
6. Tribute, service, or rent paid by a feudal tenant to a lord.
adj.
1. Made to order: custom suits.
2. Specializing in the making or selling of made-to-order goods: a custom tailor.
[Middle English custume, from Old French costume, from Vulgar Latin *cōnstūm(i)n-, alteration of Latin cōnsuētūdin-, oblique stem of cōnsuētūdō, custom, from cōnsuētus, past participle of cōnsuēscere, to accustom : com-, intensive prefix; see COM- + suēscere, to become accustomed; see s(w)e- in the Appendix of Indo-European roots.]