1. (biology) the movement of an organism either towards or away from a source of light

Encyclopedia: Phototaxis

• order Urodella
• order Uropygi
• order Urticales
• order Ustilaginales
• order Volvocales
• order Xiphosura
• order Xyridales
• order Zeomorphi
• order Zygnemales
• order Zygnematales
• order-Chenopodiales
• ordered
• ordered series
• orderer
• ordering
• orderliness
• orderly
• orderly sergeant
• ordinal
• ordinal number
• ordinance
• ordinand
• ordinarily
• ordinariness
• ordinary