Tim Bowen spares a few moments to help out with some word grammar.
The word spare functions as an adjective, a verb and, occasionally, a noun. In the latter category, it is used to mean something that you have in addition to other similar things, that you can use if you need another one, as in ‘The light bulb has just blown. It’s OK. I’ve got a spare’. It is also used to mean a spare tyre or a spare wheel, as in ‘You’ll find the spare in a compartment under the boot’.
As an adjective, spare is used pre-nominally with a range of nouns to mean an extra item or set, e.g. a spare key, spare clothes and a spare pair of glasses. If something is going spare, it is available for use if you want it, as in ‘Can I borrow these books if they’re going spare?’ or ‘Is any of that delicious-looking cake going spare?’ To go spare can also be used informally to mean to get extremely angry, as in ‘He went spare when he heard that his son had taken his car without permission’.
As a verb, spare can be used with a number of nouns to mean to prevent someone from experiencing an unpleasant, painful or embarrassing situation or feeling, as in ‘Could you at least spare me the embarrassment of having to ask you for money in public?’ If you have money, room or time to spare, you have more than enough, as in ‘We’ve got time to spare before the train leaves, so let’s go for a coffee’. If you spare no expense, you spend as much money as necessary to make something good, without worrying about the cost, as in ‘The minister said that he will spare no expense to ensure that the competition is the best ever’.