Harley-Davidson XA Into the war, the government asked Harley to build a bike that was similar to the BMWs used by the Germans. So they didâto exacting specification. The 740cc flat twin and shaft drive aped the R71 perfectly. Harley built 1,000 XAs and even used the platform to test its first telescoping fork.
Definition of atom for English Language Learners. : 1  the smallest particle of a substance that can exist by itself or be combined with other atoms to form a molecule. : 2  a very small amount of something.
Best Answer: An atom can be any one of the elements. A molecule is a combination of atoms into a single substance. A compound is a molecule that includes atoms of two different elements. Organelles are parts of cells made up of many, many atoms, such as the mitochondria. Elements are the simpliest form of complete matter, for example a single hydrogen (H) atom.