This document summarizes structural and numerical variations in chromosomes and their implications. Structural variations include deletions, duplications, translocations, and inversions which alter chromosome structure. Numerical variations include aneuploidy, involving extra or missing chromosomes, and euploidy, involving extra sets of chromosomes. Aneuploidy includes hypoploidy, hyperploidy, trisomy and tetrasomy. Euploidy includes monoploidy and polyploidy such as autotetraploid and allopolyploid. Chromosomal variations have implications for plant breeding including determining gene locations and producing new varieties with desirable traits like larger fruits or flowers.