12. The twelfth principle. An elucidation of nouns derived from doubled roots that occur with an added mem or tav at the beginning.

1. Know that nouns which occur with an added mem at the beginning are, for the most part, vocalized with a qamats on the first letter, following the pattern of nouns with a quiescent middle letter (naḥei ʿayin). However, there is a distinction between them: Those nouns of the naḥei ʿayin class typically have ḥolam in the final syllable, such as maqom, makhon, malon. By contrast, these nouns take either a qamats or a tsere in the final syllable, such as masakh and magen.

2. There is a further difference: just as nouns with a quiescent middle letter (naḥei ʿayin) normally change from a qamats to a sheva, as you already know, these do not undergo such a change. For example, from nagan one says magen, magenim, mageney. The qamats does not change. The reason is that it stands in the place of a dagesh; therefore it cannot change, just as I have said repeatedly, that forms which function as if they were dagush do not change.

3. A few are also found with mem and ḥolam, following the pattern of those whose first radical is yod. There is, however, a difference: in those cases the final vowel is either qamats or tsere, as in moshav and moqesh; whereas these have pataḥ, as in mored from the root radad, as in maʿaseh mored (1 Kings 7:29), and from rakhakh, as in va-haveti morekh (“I will bring faintness,” Lev. 26:36). These are very few.

4. However, with feminine forms they are numerous, and they are useful for identification, since they are dageshed in the middle radical (ayin), such as megillah and meḥittah; and with an added tav, such as tefillah and taḥannah. There is also a single example with an added mem at the end, namely ḥinnam, derived from the root ḥanan.