The Collaborative International Dictionary of English v.0.48:

Seven \Sev"en\, a. [OE. seven, seoven, seofen, AS. seofon,
   seofan, seofen; akin to D. zeven, OS., Goth., & OHG. sibun,
   G. sieben, Icel. sjau, sj["o], Sw. sju, Dan. syv, Lith.
   septyni, Russ. seme, W. saith, Gael. seachd, Ir. seacht, L.
   septem, Gr. ???, Skr. saptan. [root]305. Cf. Hebdomad,
   Heptagon, September.]
   One more than six; six and one added; as, seven days make one
   week.
   [1913 Webster]

   Seven sciences. See the Note under Science, n., 4.

   Seven stars (Astron.), the Pleiades.

   Seven wonders of the world. See under Wonders.

   Seven-year apple (Bot.), a rubiaceous shrub (Genipa
      clusiifolia) growing in the West Indies; also, its edible
      fruit.

   Seven-year vine (Bot.), a tropical climbing plant
      (Ipom[oe]a tuberosa) related to the morning-glory.
      [1913 Webster]