The American Heritage® Dictionary of the English Language: Fourth Edition. 2000.
Appendix I
Indo-European Roots
ENTRY:
wei-
DEFINITION:
To go after someting, pursue with vigor, desire, with noun forms meaning force, power. Related to w-ro-. 1. Zero-grade form *w- (< *wi-). vim, violate, violent, from Latin vs, force, with irregular derivatives violre, to treat with force, and violentus, vehement. 2. Suffixed o-grade form *woi()-ty-.gain1; rowen, from Old French, gaaignier,gaignier, to obtain, from Germanic *waithanjan, to hunt, plunder, denominative verb from *wai-thj, “pursuit,” hunting. 3. Suffixed zero-grade form *wi-to- becoming *w-to-.invite, from Latin invtre, to invite (in-, in; see en). (Pokorny 3. ei- 1123.)
-
-ro-. 1. Zero-grade form *w
re, to treat with force, and violentus, vehement. 2. Suffixed o-grade form *woi(
, “pursuit,” hunting. 3. Suffixed zero-grade form *wi
ei- 1123.) 
