PAL

Ptolemaeus Arabus et Latinus

_ (the underscore) is the placeholder for exactly one character.
% (the percent sign) is the placeholder for no, one or more than one character.
%% (two percent signs) is the placeholder for no, one or more than one character, but not for blank space (so that a search ends at word boundaries).

At the beginning and at the end, these placeholders are superfluous.

بسيط  ‘plane’

Arabic

References: Alm. MS Tunis: . – PH Morelon: I.12:1, 43:3
Translation of:
Greek: ἐπίπεδος [Alm. Heiberg: I.3, 13:15; I.4, 15:18]
Greek: ἐπίπεδον [PH Heiberg: I.9:1, 80:29; I.11:1, 90:10; I.12:1, 94:9]
Modern translations:
French: plan [PH Morelon: I.12:1, 42:4]
German: Ebene [PH Nix: I.12:1, 95:10]
Synonyms:
سطح[PH Morelon: I.9:1, 29:2; I.11:1, 37:17]
مسطوح[Alm. MS Tunis: ]