Size Class

Definitions

1. In memory allocators like jemalloc or tcmalloc, a predefined bucket of allocation sizes (e.g., 8, 16, 32, 64 bytes) used to reduce fragmentation by rounding requests up to the nearest class. In iOS/UIKit, a trait that categorizes a view's available space as compact or regular to drive adaptive layout decisions.

   In plain English: A category that groups things by size — either memory chunks into standard buckets for efficiency, or screen space into 'small' and 'large' for layout decisions.

   Example: "On iPad in landscape, the horizontal size class switches to regular, so we show the split-view navigation."

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