The Collaborative International Dictionary of English v.0.48:

Yea \Yea\ (y[=a] or y[=e]; 277), adv. [OE. ye, ya, [yogh]e,
   [yogh]a, AS. ge['a]; akin to OFries. g[=e], i[=e], OS., D.,
   OHG., G., Dan. & Sw. ja, Icel, j[=a], Goth. ja, jai, and
   probably to Gr. "h^ truly, verily. [root]188. Cf. Yes.]
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   1. Yes; ay; a word expressing assent, or an affirmative, or
      an affirmative answer to a question, now superseded by
      yes. See Yes.
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            Let your communication be yea, yea; nay, nay.
                                                  --Matt. v. 37.
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   2. More than this; not only so, but; -- used to mark the
      addition of a more specific or more emphatic clause. Cf.
      Nay, adv., 2.
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            I therein do rejoice, yea, and will rejoice. --Phil.
                                                  i. 18.
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   Note: Yea sometimes introduces a clause, with the sense of
         indeed, verily, truly. "Yea, hath God said, Ye shall
         not eat of every tree of the garden?" --Gen. iii. 1.
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The Collaborative International Dictionary of English v.0.48:

Yea \Yea\, n.
   An affirmative vote; one who votes in the affirmative; as, a
   vote by yeas and nays.
   [1913 Webster]

   Note: In the Scriptures, yea is used as a sign of certainty
         or stability. "All the promises of God in him are yea,
         and in him Amen." --2 Cor. i. 20.
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WordNet (r) 3.0 (2006):

yea
    adv 1: not only so, but; "I therein do rejoice, yea, and will
           rejoice" [syn: yea, yeah]
    n 1: an affirmative; "The yeas have it" [ant: nay]