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