Jacob ( /ˈdʒeɪkəb/; Hebrew: יַעֲקֹב‎‎ Standard Yaʿakov, Tiberian  Yaʿăqōḇ (help·info); Septuagint Greek: Ἰακώβ Iakōb; Arabic: يَعْقُوب‎ Yaʿqūb; "heel" or "leg-puller"), also later known as Israel (Hebrew: יִשְׂרָאֵל‎‎, Standard Yisraʾel, Tiberian Yiśrāʾēl; Septuagint Greek: Ἰσραήλ Israēl; Arabic: إِسْرَائِيل‎ Isrāʾīl; "persevere with God"), as described in the Hebrew Bible, the Talmud, the New Testament and the Qur'an was the third patriarch of the Hebrew people with whom God made a covenant, and ancestor of the tribes of Israel, which were named after his descendants.

In the Hebrew Bible, he is the son of Isaac and Rebekah, the grandson of Abraham and Sarah and of Bethuel, and the younger twin brother of Esau. Jacob had twelve sons and at least one daughter, by his two wives, Leah and Rachel, and by their female slaves Bilhah and Zilpah. The children named in Genesis were Reuben, Simeon, Levi, Judah, Dan, Naphtali, Gad, Asher, Issachar, Zebulun, daughter Dinah, Joseph, and Benjamin.

Before the birth of Benjamin, Jacob is renamed "Israel" by an angel (Genesis 32:28-29 and 35:10). The name "Israel" can be translated as "God contended", but other meanings have also been suggested. Some commentators say the name comes from the verb śœarar ("to rule, be strong, have authority over"), thereby making the name mean "God rules" or "God judges". Other possible meanings include "the prince of God" (from the King James Version) or "El fights/struggles".

Jacob Christian Hansen Ellehammer (June 14, 1871 – May 20, 1946) was a Danish watchmaker and inventor born in Bakkebølle, Denmark. He is remembered chiefly for his contributions to powered flight.

Following the end of his apprenticeship as a watchmaker he moved to Copenhagen where he worked as an electronics mechanic before establishing his own company in 1898. In the beginning he produced cigarette machines, beverage machines and other electronic machinery. In 1904 he produced his first motorcycle, the Elleham motorcycle. In 1905, he constructed a monoplane, and in the following year a "semi-biplane". In this latter machine, he made a tethered flight on 12 September 1906.

Ellehammer's later inventions included a successful triplane and helicopter. His helicopter was a coaxial machine. A famous photo shows it hovering in 1914, though there is no evidence that it was successful in achieving translational flight. Ellehammer later studied a disc-rotor configuration - a compound helicopter with coaxial blades that extended from the hub for hover, and retracted for high speed vertical flight. Although a wind tunnel model was constructed, there's no evidence that anything more was studied.