"Annual income twenty pounds, annual expenditure nineteen nineteen and six, result happiness. Annual income twenty pounds, annual expenditure twenty pounds ought and six, result misery". On the 200th anniversary of Charles Dickens' birth, today I am taking Mr Micawber's famous piece of advice in David Copperfield as inspiration.
'Ought' in this quotation means "nought" ('no shillings' is meant). It's not very common to hear 'ought' in this sense today, although I remember my dad saying it 30 or 40 years ago in connection with small measurements - one point ought six, that sort of thing. Ought is a variation of nought; it just lost the N a couple of hundred years ago. This process occurred with other common words, too; an adder, a snake, was spelled nædder in Old English and nadder in Middle English. Since "a nadder" sounds exactly the same as "an adder" the n eventually migrated across to the article. Apron was originally napperon (it comes from the French nappe, tablecloth) and orange can be ultimately traced back through the Persian nārang and the Sanskrit nāraṅga.
A similar word is "naught", not very common in Britain these days except in the phrase "come to naught" (and many people spell that 'nought'). It's a very old word that goes back to the beginnings of English, and is a mixture of no + wight, or ne + aught, both wight and aught meaning 'thing' in Old English, so naught was 'no thing', or 'nothing'. Naught and nought were originally pronounced differently, but by the 17th century the vowel sounds had merged to sound the same - in standard English, that is - note the regional word 'nowt', still pronounced with the original pronunciation. Naught and nought could also be used interchangeably, but naught tended to be associated with the sense 'worthless' or 'bad'. This is how the word naughty came about (there was once also the spelling noughty).
Aught is the opposite of naught, and means 'anything'. It is not very common in British English these days, except for the phrases "for aught I know" and "for aught I care".