Per Random House Webster's College Dictionary, Ed. 1991,
suitable or ready for use; of use or service; at hand: I used whatever tools were available.
readily obtainable; accessible: available resources.
sound; just; well-founded: a valid reason.
producing the desired result; effective: a valid antidote for gloom.
having force, weight, or cogency; authoritative.
legally sound, effective, or binding; having legal force: a valid contract.
Per Collins-Robert English-French Ditionary, Ed. 1985,
(a) [material, people] disponibilité f
(b) (US: validity) validité f
(a) personnel disponible; thing disponible, utilisable
(b) (US: valid) valable, valide (for pour)
My question is, what's the difference between "available" and "valid" in the sense "having sufficient power or efficacy"?
In addition, absent clear context, "can't the word "available" sound sort of ambiguous as to whether it's "obtainable/accessible" or "having sufficient power or efficacy" that actually is meant?
Please, consider the following example:
The period for which these tickets are available is 3 months
The period of availability for these tickets is 3 months
could be understood as meaning,
The period for which these tickets are obtainable/accessible is 3 months
The period for which these tickets are valid (=effective) is 3 months