The sonnet belongs to a collection, indeed the title is composed by a number (20). The collection, written by Shakespeare, puts together 154 sonnets.The structure of the sonnet follows the Shakespearian model ( called also Elisabethian one): it is organized into three quatrains and one rhyming coulplet.The first and second quatrains start with the undetermined article "a/an" and the third one with the word "and"; so it gives to sonnet unity and syntactic coherence.The reader can understand there is also semantic coherence among the quatrains: they are the exaltation and glorification of the speaking voice's Fair youth. During all quatrains, the speaking voice compares him to women. So thw reader may be curious to find out the reason of this choice.In the first line of first quatrain the speaking voice compares the fair youth's face to a face of woman. This choice can be justified if the reader bears in mind that in renaissance ideology (and in the previous one) beauty was embodied by woman.So the speaking voice glorifies beuty of fair youth's face. Moreover he adds the fair youth was made up by nature's hand, so it gives  a characterization more pure and perfect to fair youth's imagine.The reader can find the verb and the subject of the first line (so of the first proposition) in the second one. So the speaking voice creates a continuity between the first and the second proposition. Indeed there isn't a full stop beetween them.The second line underlines the complate subjugation of the speaking voice.The third line starts with word " a" and it confers unity to the first quatrain . The speaking voice compares the fair youth's heart to heart of a woman, but he adds his fair youth isn't acquainted with shifting change, so he is faithful.So after he has conneted his fair youth to all the positive qualities of women he underlines him hasn't some of women's lacks: he is also faithful.Shakespeare is careful to underline he is talking about the false women not whole ones.The second quatrain is the  the continuation of the last line of first quatrain. So the second one is the continuation of first one.The speaking voice remarks  better qualities of his fair youth than the false women: the fair youth's eye brights more than them's one and he is faithful. The argument of faithful is represented again but with one other imagine.Moreover the speaking voice connotes the eye of fair youth as shining. So he underlines the importance of fair youth to him. This thesis is confirmed into the following line.The last line of second quatrain finishes the description of fair youth; the proposition is the resume of the two quatrains and the start of new argument: the speaking voice underlines that all these attributes give him the possibility to be loved by women and men.The third quatrain is an explanation of this statement : the fair youth was made up to be a woman but the Nature(with capital n becuse is a perfonification) falls in love thanks to his beauty and his attributes (connoting in the first and second quatraib). So she gives him private parts of male.The rhyming couplets conclude the discourse of the speaking voice: because of the Nature gives him that quality and thanks to his beauty and his attributes the fair youth can satisfy women and can be loved to speaking voice.