Genetic modification - transgenesis?

Transgenesis and genetic modification are overlapping concepts so in many cases both terms could apply to the same situation. Transgenic organisms are those that have had a gene that is from another species added to their genome. Genetic modification includes transgenesis but also other changes to an organism's genes that change a gene's sequence without adding any foreign DNA. So removing a copy of a gene from a species, modifying it and returning it would be genetic modification. Replacing it with a similar gene from another species would be both genetic modification and transgenesis.