- The layer of wood formed in a plant during a single year. Annual rings appear concentric when viewed in cross section.年轮：一年里树木长出的层。从截面上看年轮呈同心圆状
- extraditing
- extradition
- extraditions
- extrados
- extradoses
- extraembryonal
- extraembryonic
- extragalactic
- extrahepatic
- extra-high voltage
- extrajudicial
- extralegal
- extramarital
- extramundane
- extramural
- extramusical
- extraneous
- extranet
- extranets
- extranuclear
- extraocular muscle
- extraordinaire
- extraordinary
- extrapolate
- extrapolated