The first part of a brachiopod (Brachiopoda) or bivalve (Bivalvia) shell to be formed. In a brachiopod, the umbo is the posterior part of each valve; in a bivalve it forms the dorsal part of the shell.
Umbo
- gypcrete
- gypsic
- gypsisols
- gypsum
- gyrator
- gyre
- gyrocompass
- gyroconic
- gyrofrequency
- gyrogonite
- gyromagnetic ratio
- gyroremanent magnetization
- gyroscope
- gyroscopic sensor
- gyrostabilized binoculars
- gyrosynchrotron radiation
- gyttja
- gz
- Gzelian
- Gzhelian
- GZK limit
- Gómez, Juan Vicente (1864–1935)
- Göbbels, Joseph
- Gödel-Gentzen translation
- Gödel, Kurt