The Crowns of Hebrew Script
The gemara in Menachot (29b) introduces the halakha of "ziyunin." The gemara cites Rava, who requires three ziyunin (so named for their resemblance to the letter zayin, and more commonly known in halakhic literature as "taggin," or miniature crowns) on the tops of seven letters: shin, ayin, tet, nun, zayin, gimmel, and tzadi. These strokes are clearly meant to embellish the print of a Torah scroll or tefillin. To what extent, however, do we view these taggin as an essential part of the letter? Do we define them as independent marks merely appended to the letter in an attempt to adorn the print of sacred texts, or do we regard them as an integral extension of the script?
Possibly the most compelling statement regarding the integration of these marks can be found in the gemara on Shabbat 104b-105a, which implies that one who writes these letters on Shabbat without applying these lines has not violated the biblical proscription of writing on Shabbat. Such a bold statement, taken at face value, would immediately assume these marks to be essential parts of the letters; without them halakhic letters have not been written.
In fact, this conclusion would be so powerful and revolutionary that many Rishonim adopt interpretations which stop short of such a position. According to some, the gemara is only referring to someone writing a Torah scroll; in such an instance the work would be incomplete without these marks. Some suggest that in theory letters without the marks are considered halakhically viable; however, since the scribe intended to append these marks and failed to do so, he has not performed an purposeful Shabbat violation and cannot be punished. Thus, though the simple reading of the gemara yields a perspective of taggin as essential aspects of the letters, some Rishonim reinterpret the scenario in a manner which suggests otherwise.
In terms of the halakhic consequences of this question, the most central question involves the status of letters without these marks: if tefillin, for example, were written without these taggin, would they be valid? The Rosh, in his commentary to Hilkhot Tefillin (found after Menachot), cites, in the name of the Shimusha Rabba, a list of letters from the texts of tefillin which require taggin. Subsequently, the Rosh comments that this list refers to larger taggin (which are not mentioned at all in the gemara), and he sees no reason that the absence of these larger forms of taggin should invalidate letters. The distinct impression from the Rosh's statements is that the smaller taggin (mentioned by the gemara pertaining to the seven aforementioned letters) do indeed entail a fundamental component of letters and that their absence would invalidate. By contrast, the Rambam in Hilkhot Sefer Torah (7:3) states clearly that the absence of taggin never invalidates letters.
A second question would relate to the scope of these taggin. Would, for example, taggin be necessary when writing a bill of divorce bill ("get")? The Mardekhai in Gittin (316) cites two positions in the Rishonim, and it is quite clear that if these taggin are an essential component of letters (as suggested by the previously mentioned gemara in Shabbat), then they should be included when writing a get.
The Rambam, Hilkhot Tefillin (5:1), establishes that the writing of the mezuza must be sequential, a halakha known as "ke-sidran." If the sofer makes a mistake and continues writing, he cannot go back and correct his error, but must instead write an entirely new mezuza. What would happen if a sofer omitted taggin from a letter of a mezuza, and after finishing succeeding sections the scribe returned to add these taggin? Would these additions violate the principle of ke-sidran? The Bach in Orach Chayim 36 claims that the ke-sidran principle would not be violated; apparently, he does not view taggin as essential elements of the script.
Another interesting question surrounds the shape of these additions. The gemara, as we noted above, actually employs the term "ziyunin," suggesting a shape resembling the letter zayin. In fact, the Rambam in Hilkhot Tefillin 2:8 describes the tag as a standing zayin. The Beit Yossef (Orach Chayim 36) cites in the name of the Agur to follow the Rambam's ruling, and many Sephardic soferim follow this custom. [By granting these strokes an actual independent shape - the letter zayin - can we still view these taggin as integral parts of the base letter?] Rashi's comments (Menachot 39b), however, suggest that these taggin were not actually given independent form, and they certainly were not meant resemble an independent letter.
An even more compelling assessment of taggin emerges from an interesting conclusion cited by the Mardekhai in Menachot (553): some scribes omitted taggin and instead relied upon the integral boundaries and corners of the letters. This approach views the taggin as playing a functional, rather than aesthetic, role. They were instituted, this view implies, in order to ensure precise and bounded letters with sharp corners, rather than rounded curves. The tops of these seven letters are made "crisp" through the insertion of taggin. A sofer who is able to write these "crisp" letters without the use of taggin is excused from including them. See in addition the Beit Yossef, Orach Chayim 36, who cites a position which validates letters without taggin as long as the tops are sharp and not round. In fact, some Rishonim cite the custom to place the taggin on the outer corners of the tops of these letters; such placement would indeed suggest that taggin serve to bound the corners of the tops of these seven letters. This stance clearly views the taggin as integral aspects of the letters which serve a distinct functional role.
We have thus seen that the taggin, the crowns of certain letters in formal Hebrew script, can assume either of two roles: additional adornments or integral improvements. This distinction of purpose has ramifications in many areas, including the shape and placement of these crowns and the scope and nature of the requirement to add them.