The term 'one by one' can be expressed in four different ways, EACH with a different number of letters. The first is 'seriatim', which has 8 letters. This term is derived from Latin and means 'in a series'. The second is 'ELEVEN', which has 6 letters. This is a number that is one more than ten. The third is 'EACH', which has 4 letters. This word is used to refer to every single one of a group of people or things. Finally, the fourth is 'SINGLY', which also has 6 letters. This term means 'INDIVIDUALLY' or 'SEPARATELY'.