a. An apartment or dwelling situated on the roof of a building.
b. A residence, often with a terrace, on the top floor or floors of a building.
c. A structure housing machinery on the roof of a building.
2. A shed or sloping roof attached to the side of a building or wall.
3. Sports The sloping roof that rises from the inner wall to the outer wall surrounding three sides of the court in court tennis, off which the ball is served.
[Alteration of Middle English pentis, pentace, a shed attached to a wall of a building, from Anglo-Norman pentiz, penthouses, from Old French apentiz, penthouse, from apent, past participle of apendre, to belong, depend, from Medieval Latin appendere, from Latin, to hang, suspend; see APPEND.]
Word History: The status of the word penthouse has risen considerably in its history. The word ultimately goes back to Latin appendere, "to cause to be suspended." In Medieval Latin appendere developed the sense "to belong, depend," a sense that passed into apendre, the Old French development of appendere. From apent, the past participle of apendre, came the derivative apentiz, "low building behind or beside a house," and the Anglo-Norman plural form pentiz. The form without the a- was then borrowed into Middle English, giving us pentis, which was applied to sheds or lean-tos added on to buildings. Because these structures often had sloping roofs, the word was connected with the French word pente, "slope," and beginning in the 1500s, the second part of the word began to be associated with the word house, in its meaning "a building for human use," and spellings like penthouse begin to become common. The use of the term with reference to fancy apartments developed from its application to a structure built on a roof to cover such things as a stairway or an elevator shaft. Penthouse then came to mean an apartment built on a rooftop and finally the top floor of an apartment building.
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