The term 'saying nothing' can be expressed in four different ways, each with a different number of letters. The first is 'TACIT' with five letters, which means to express something without words. The second is 'SILENT' with six letters, which means to not make any sound. The third is 'MUM' with three letters, which is an old-fashioned way of saying SILENT. The fourth is 'MUTE' with four letters, which means to not be able to speak. All four terms refer to the same concept of saying nothing.