Lexicon Browse - O
Oak gall (Gallnut) - see GallnutObliques - Angular letter strokes.Occupational calendar - A calendar incorporating a series of illustrations that depict the labors appropriate to each of the months.Octateuch - The first eight books of the Old Testament.Octavo - The format of a volume created by folding a sheet three times to create a quire of eight leaves (16 pages),Office - see Divine OfficeOffset - The transfer of ink or paint from one page to the facing page.Oklad - an alternative Russian term for riza. See Riza.Opening title - see IncipitOrdinal - A guide to the celebration of the liturgy, usually including instructions for liturgical actions to be carried out by the clergy.Origin - The place a manuscript was made.Ornament - A decorative element applied to a manuscript page.Orpiment - A yellow pigment used in inks.Orthography - The spelling of words as practiced in a manuscript, which may be useful in placing its origin.Otiose stroke - A stroke added to a letter for decorative purposes.Outline drawing - A style of illumination in which only the outlines of the figure or object are drawn, in black or colored ink.Overpainting - The finished painting that is executed over a drawing or preliminary underpainting.Ownership inscription - see ProvenanceOxidation - A chemical reaction resulting from exposure to oxygen.