The best replacement for validity is reliability.

The best alternatives to validity are rated as following:
★★★★★  reliability
★★★  accuracy
★★★  soundness
★★★  external validity
★★  truth
★  utility
★  precision
★  construct validity
★  content validity
★  reliability assessment
★  internal validity
  reliability psychology
  reliability science
  cogency
  generalizability
  reliability examples
  reliability research
  veracity
  test reliability
  reliability more important
  validation
  convergent validity
  credibility
  reliable
  criterion validity
  instrument validity
  face validity

Your alternative for validity is not listed? Suggest!
Speaking about validity, one probably shouldn't forget about reliability.

Other search terms related to validity and their ratings are:
★★★★★ reliability
★★★★ both predictive validity and construct validity
★★★ external validity
★ internal validity
★ predictive validity
experiment
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Google Trends

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validity
reliability
accuracy