Deficiency/dɪˈfɪʃnsi/ Definition 1 of 4Pro Tip 1/3Common Pairings Often used with 'vitamin' and 'mineral', to describe health-related lacks. She's been diagnosed with a mineral deficiency. Pro Tip 2/3Quantifiable Lack It implies you can measure what is missing. A deficiency of three units was noted in stock. Pro Tip 3/3Negative Consequence Use 'deficiency' when the lack of something leads to negative outcomes. A deficiency in attendance could lead to course failure.