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• The basic multilingual plane (BMP, or Plane 0) contains the common-use characters for all the modern scripts of the world as well as many historical and rare characters.

• In the supplementary multilingual plane (SMP, or Plane 1) characters are encoded for scripts or symbols which would not fit into the BMP or occur only infrequently. These include many historic scripts, some notational systems, and a few historic extensions of scripts otherwise encoded in the BMP.

• The supplementary ideographic plane (SIP, or Plane 2) is intended for CJK characters [Chinese, Japanese, Korean; really CJKV, including Vietnamese] which did not fit into the BMP.

• The tertiary ideographic plane (TIP, or Plane 3) received CJK Unified Ideographs Extension G (30000–3134F) with Unicode 13.0.0, in March 2020.

Planes 4 Planes 3 to 16 are either not yet used, or are intended for special purposes [Plane 14] or for private use [Planes 15 and 16].

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Note that Brill publications routinely contain characters from three four planes: BMP, SMP, SIP, and SIPTIP. This means that all software used in handling Brill data must be capable of processing characters from all planes of Unicode, not just of Plane 0!

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