Mode is most frequent value. May not exist (no repeats) or multiple modes. Example: {1, 2, 2, 3, 3, 3, 4} → mode = 3 (frequency 3). {1, 2, 3, 4} → no mode. {1, 1, 2, 2, 3} → bimodal (modes 1, 2). For grouped data: Mode = L + [Δ₁/(Δ₁ + Δ₂)] × w, where L = lower class of modal class, Δ₁ = difference with previous class frequency, Δ₂ = difference with next class, w = width. Advantages: Represents most common value; works for qualitative data. Disadvantages: May not exist; ignores other frequencies. Exam tip: Identify highest frequency. Handle multimodal carefully. Use for preference/category data.