C1[U]the need for something: You can come early if you want to, but there's no necessity for it.[+ to infinitive]Is there any necessity to reply to her letter?The report stresses the necessity of eating plenty of fresh fruit and vegetables.With a personal fortune of six million pounds, she certainly doesn't work out of necessity (= because she needs to).We'll employ extra staff to help out as and when the necessity arises(= when we need to).Essential or necessaryC1[C]something that you need, especially in order to live: We brought only the bare necessities with us.He regarded music as one of life's necessities.Essential or necessary