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.

plan ‘plane’

French

References: PH Morelon: I.11:1, 36:22; I.12:1, 42:4
Translation of:
Arabic: سطح [PH Morelon: I.9:1, 29:2; I.11:1, 37:17]
Arabic: بسيط [PH Morelon: I.12:1, 43:3]