mast(o)-of or pertaining to the breast: Greek μαστός (mastós), breast, woman's breast, man's pectoral muscle mastectomy: meg(a)-, megal(o)-, -megaly: enlargement, million Greek μέγᾰς (mégas), big, large, great, mighty splenomegaly, megameter: melan(o)-having a black color Greek μέλᾱς, μελανο-(mélās, melano-), black, dark melanin

What does Masto mean? Masto- is a combining form used like a prefix meaning “breast.” It is often used in medical terms, especially in anatomy and pathology. Masto- comes from the Greek mastós, meaning “breast.” The Latin-based analog to masto- is mammo-, from mamma, meaning “breast.”.

You don't need to do Medical Terminology, but it does help, especially since you'll already know what distal/proximal, ventral/dorsal, etc. are. Bonus points if you take a class that makes you decline nouns in medical Latin...

a. A vertical structure consisting of a spar or several spars affixed end-to-end, rising from the keel or deck of a sailing vessel to support the sails. b. A single spar serving as a part of such a structure: the fore topgallant mast. 2. a.