 Advances in technology are often responsible for the coinage of retronyms.For example, the term "acoustic guitar" was coined with the advent of electric guitars; analog watches were renamed to distinguish them from digital watches once the latter were invented; "association football" was coined to distinguish from the later sports of rugby football and gridiron football; and "push bike" was created to distinguish from motorbikes and motorized bicycles.The first bicycles with two wheels of equal size were called "safety bicycles" because they were easier to handle than the then-dominant style that had one large wheel and one small wheel, which then became known as an "ordinary" bicycle.