One and one half.
[Latin semi-, a half, plus que, and.]
A sesquicentenary is the one hundred and fiftieth anniversary of a significant event; a sesquialtera (Latin alter, second) in music denotes a ratio of 3:2, as in an interval of a fifth. A sesquioxide is one in which oxygen is present in the ratio of three atoms to two of another element, as for example aluminium oxide, Al2O3; a sesquiterpene is a member of the terpene family of volatile unsaturated hydrocarbons found in essential oils that has one and a half times as many carbon atoms (15) as a terpene (10). A sesquipedalian word (Latin sesquipedalis, a foot and a half long) has many syllables; the adjective also describes somebody long-winded or who uses long words.