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.

dans lequel ne se présente aucun mélange avec d'autres ‘unmixed’

French

References: PH Morelon: I.5:1, 20:20
Translation of:
Arabic: الذي لا يخالطه غيره  [PH Morelon: I.5:1, 21:13]