Commentary for Shevuot 6:2

With money, how is the woman betrothed?, he gives her, in front of 2 witnesses a 'Pruta' or something worth 'the value of a pruta' and says, "Harei At Mekudeshet Li BaZeh" (With this, you are betrothed to me). [Rama: and there are those who say that he should add to this "according to the daat (religion) of Moses and Israel," and it is customary, a-priori, to betroth her with a ring, and there is a reason for this from the Tikunei Zohar (that the ring needs to be round with no breaks, like the letter "Samach" ed.)] And this is the same law if he said to her, "Harei you are... 'engaged to me,' or 'you are to me for a wife,'..." and the same for any language that have the essence of certain language of betrothal in that region and ONLY if she clearly understands that this is language of betrothal and if he spoke of marriage with her beforehand about the business of marriage and he gave her the gift (Pruta or Sheva-Pruta), then even in silence (and in front of two witnesses), she is betrothed. And if he is he is still involved in the same subject (of marriage), and of course, if he uses a certain language of betrothal, rather she does not (completely) understand his exact words, they are still betrothed. [Rama: Some say that the subject about which they are speaking is not necessarily marriage itself, rather they are speaking of subjects related to the subject of marriage and not about betrothal directly, rather they are speaking about the needs of the couple's relationship. And other say that it is not this subject about which they he is speaking with her, rather all the discussion before (he gives her the pruta) that apply in this matter.]