Homologous series

A homologous series is a group of molecules that all have the same structure, but each one has one more atom or group of atoms than the last. Think of it like a staircase, each step has the same structure, but it's just one step bigger than the step before it. There are lots of different kinds of homologous series, like the fatty acids in cooking. They all have the same parts, but one more Carbon atom is added to each one, so each one is just a bit bigger than the one before it.