[val.id] adj [MF or ML; MF valide, fr. ML validus, fr. L, strong, fr. valere] (1571) 1: having legal efficacy or force; esp: executed with the proper legal authority and formalities "a ~ contract"
2. a: well-grounded or justifiable: being at once relevant and meaningful "a ~ theory" b: logically correct "a ~ argument" "~ inference"
3: appropriate to the end in view: effective "every craft has its own ~ methods"
4. of a taxon: conforming to accepted principles of sound biological classification -- va.lid.i.ty n -- val.id.ly adv syn valid, sound, cogent, convincing, telling mean having such force as to compel serious attention and usu. 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".