\Thir"ty\, a. [OE. thritty, AS. [thorn]r[=i]tig,
[thorn]rittig; akin to D. dertig, G. dreissig, Icel.
[thorn]rj[=a]t[=i]u, [thorn]rj[=a]tigi, [thorn]rir teger,
Goth. [thorn]reis tigjus, i.e., three tens. See {Three}, and
Ten, and cf. {Thirteen}.]
Being three times ten; consisting of one more than
twenty-nine; twenty and ten; as, the month of June consists
of thirty days.

\Thir"ty\, n.; pl. {Thirties}.
1. The sum of three tens, or twenty and ten; thirty units or
   objects.

2. A symbol expressing thirty, as 30, or XXX.