According to Rashi's opinion in Chumash, Rivka was three years old when she married Yitzhak. The Torah uses the word na/arah to describe her. But a na'arah is twelve to twelve and one-half years old. This does not seem to conform to that definition of na'arah.
According to the third Tosafot on Amud Bet, Rivka was fourteen years old when she married Yitzhak. But the Torah uses the word betulah to describe her. According to the Gemorrah, a betulah is under the age of bagrut, i.e., under twelve and one-half years old, and once she attains the age of twelve and one-half years she is called a bogeret. Tosefot's opinion also does not seem to conform to the words in the posuk.
It seems that the only way to explain these difficulties with the language of the posuk is to define these words in the posuk other than in accordance with the way in which they are defined in the posuk.
Is there any other explanation?
Michael S. Winokur, Forest Hills, New York, U.S.A.
Let us relate to your second question first. Ramban (Chidushei Yevamos) explains that Na'arus is the six-month period which follows Katnus, which ends with the development of Simanim. If Simanim appear only at a later age than twelve, Na'arus commences then. It is therefore possible that Rivka was a Na'arah at age fourteen, and not yet a Bogeret.
Your first question is actually one of the reasons given by the Rishonim to favor the version that Rivka was fourteen over the version that she was three. However, Tosefos on 64a brings the opinion of the Gemarah that in early generations women were able to bear children at an early age. The ability to bear children is considered proof of Gadlus (see 12b) and therefore the title Na'arah would apply.
DOV ZUPNIK
However this is not an answer to Rashi who writes clearly Breishis 25:26 that she was not able to bear children until 13.
True. According to Rashi we must say that the Pasuk used the word Na'arah in it's alternative form - youth, as in 1Shmuel 1,24. See Sefer Shorashim of the Radak, "Na'ar," for other examples.
Dov Zupnik
As for Rashi's Shita see also Mlochim 2 5:2 (however there if Teitch of Na'ara is youth Ktana is extra, perhaps the change from Na'ara to Riva is to underline that it is not a Halachic Na'ara Davka, compare with Rashi Breishis 18:21 and Rashi D"H Rvisa Sanhedrin 109b). However see the Mizrachi and other Mforshim on Rashi Breishis 37:2 (also 41:12) that Rashi's question was
Mitzad haHalacha.
Kol Tuv
Yitzchok Zirkind