  The algebraic degeneracy of holomorphic curves in a semi-Abelian variety
omitting a divisor is proved (Lang's conjecture generalized to semi-Abelian
varieties) by making use of the {\it jet-projection method} and the logarithmic
Wronskian jet differential after Siu-Yeung. We also prove a structure theorem
for the locus which contains all possible image of non-constant entire
holomorphic curves in a semi-Abelian variety omitting a divisor.
