An ideogram or ideograph is a graphic symbol that represents an idea or concept, independent of any particular language, and specific words or phrases. Some ideograms are comprehensible only by familiarity with prior convention; others convey their meaning through pictorial resemblance to a physical object, and thus may also be referred to as pictograms. Pictography is a form of writing which uses representational, pictorial drawings, similarly to cuneiform and, to some extent, hieroglyphic writing, which also uses drawings as phonetic letters or determinative rhymes. Linear A is one of two currently undeciphered writing systems used in ancient Greece (Cretan hieroglyphic is the other). Linear A was the primary script used in palace and religious writings of the Minoan civilization. It was discovered by archaeologist Sir Arthur Evans. It is the origin of the Linear B script, which was later used by the Mycenaean civilization.