The term PART LEAF is composed of two words, MIDRIB and LEAF. MIDRIB is a 6-letter word that refers to the central vein of a LEAF, which runs from the stem to the tip of the LEAF. It is also known as the midvein or primary vein. The LEAF part of the term refers to the flat, green structure of a plant that is typically used for photosynthesis. Together, the two words form the term PART LEAF, which refers to the parts of a LEAF.