-decker
adjective
 (in combination) having a certain specified number of levels or layers
⇒ 
a double-decker bus
-deckera word element meaning 'level':  ◆ a double-decker bus.
-decker
                combining form
     -          having a specified number of decks or layers表示“有…层甲板的”, “…层面的”:
-       double-decker.