From WordNet (r) 3.0 (2006) [wn]:
thirty
adj 1: being ten more than twenty [syn: thirty, 30, xxx]
n 1: the cardinal number that is the product of ten and three
[syn: thirty, 30, XXX]
From The Collaborative International Dictionary of English v.0.48 [gcide]:
Thirty \Thir"ty\, a. [OE. thritty, AS. [thorn]r[imac]tig,
[thorn]rittig; akin to D. dertig, G. dreissig, Icel.
[thorn]rj[=a]t[imac]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.
[1913 Webster]
[1913 Webster]
From The Collaborative International Dictionary of English v.0.48 [gcide]:
Thirty \Thir"ty\, n.; pl. Thirties.
1. The sum of three tens, or twenty and ten; thirty units or
objects.
[1913 Webster]
2. A symbol expressing thirty, as 30, or XXX.
[1913 Webster]