Meaning of “valid” - Learner’s Dictionary

valid

adjective uk us /ˈvælɪd/
GOOD REASONS

B2 based on good reasons or facts that are true:

a valid argument
DOCUMENT

B2 A valid ticket or document is legally acceptable:

The ticket is valid for three months.
→ Opposite invalid
validity uk us /vəˈlɪdəti/ noun [ U ]

(Definition of “valid” from the Cambridge Learner’s Dictionary © Cambridge University Press)