cogent

valid, sound, cogent, convincing, telling mean having such force as to compel serious attention and usually acceptance. valid implies being supported by objective truth or generally accepted authority <a valid reason for being absent> <a valid marriage>. sound implies a basis of flawless reasoning or of solid grounds <a sound proposal for reviving the economy>. cogent may stress either weight of sound argument and evidence or lucidity of presentation <the prosecutor's cogent summation won over the jury>. convincing suggests a power to overcome doubt, opposition, or reluctance to accept <a convincing argument for welfare reform>. telling stresses an immediate and crucial effect striking at the heart of a matter <a telling example of bureaucratic waste>.