co·gent 
(kōjənt)
(kōjənt)adj.
Appealing to the intellect or powers of reasoning; convincing: a cogent argument. See Synonyms at valid.
[Latin cōgēns, cōgent-, present participle of cōgere, to force : co-, co- + agere, to drive; see ag- in the Appendix of Indo-European roots.]
cogen·cy (-jən-sē) n.
cogent·ly adv.
- protistan
- protistology
- protium
- proto-
- Proto-Algonquian
- protoceratops
- protocol
- protocolar
- protocolary
- protoctist
- protoderm
- protodermal
- protogalaxy
- Proto-Germanic
- protogynous
- protogyny
- protohistorian
- protohistoric
- protohistory
- protohuman
- Proto-Indo-European
- protolanguage
- protolithic
- protomartyr
- protomorph