What is the "other" memory?

The "other" memory is the memory which is allocated but which iOS doesn’t categorize into any of the other memory groups. In other words,

Other = Total – Free – Wired – Active – Inactive

This is iOS specific – under OS X all the memory is split between the remaining categories and "other" is always 0. Apple does not document what this memory is used for – there are opinions it is used for textures but I have not seen any confirmation or proof of this claim.

The amount of the "other" memory is usually largest of all the categories, often more than 50% of the total memory.