the state of having the same written form; homonymy or homomorphy

An organism, substance, or linguistic form that shares the same shape, structure, or written form as another; (linguistics) homograph

a word that is written the same way as another word but has a different meaning; homonym

Words that are written with the same characters but have different meanings; they may or may not share the same pronunciation

a chemical substance or mineral that shares the same crystalline structure and form as another substance despite having a different chemical composition