Unit/ˈjuːnɪt/ Definition 1 of 5Pro Tip 1/2Part of Whole Identify 'unit' as a part that makes up something larger, like building blocks. Each classroom is a unit of the entire school. Pro Tip 2/2Measurement Context Used in context of quantity or measurement, 'unit' is often linked with numbers. Please buy two units of apple juice from the store.