Assume a word form F coding a certain value V of some morphological category C, but F contains no morph exclusively constituting the significans for V. The following subcases are to be distinguished:
V is merged with the value W of another morphological category in one morph.
. lauda-mini Latin praise-2.PL.PASS you are praised For instance in , the morph -mini not only codes person and number of the subject, but also passive voice of the verb. In this case, the labels of V and W are separated by a full stop in the gloss, according to Rule 24.
In the paradigm of C, the value V has zero expression. This is the case of the zero morph or morpheme (morphological glossing does not distinguish these two cases).1 There are three solutions for this kind of situation:
If one believes (true to markedness theory) that there is no significatum of V, then there is no morph at all. Then there is no tense, person and number in , no case and number in and no tense, mood and voice in .
. busca Spanish search searches . Herr German master.M master . mone-t Latin warn-3.SG warns If one believes that such word forms do convey the morphological values in question, one represents V in the gloss as in ', ' and '. The requirement of Rule 3 is then fulfilled by enclosing V in parentheses. These warn the reader and the parsing algorithm that T contains nothing corresponding to what they enclose.
'. busca Spanish search(PRS.3.SG) searches '. Herr German master.M(NOM.SG) master '. mone-t Latin warn(PRS.IND)-3.SG(ACT) warns Rule 22. A gloss of a linguistic unit not represented in T is enclosed in round parentheses (()).
Finally, one may believe that such forms contain zero morphs or morphemes and consequently posit a ∅ in T, as in '' and ''. This zero is then glossed like an overt morph.
''. Herr-Ø German master.M-NOM.SG master ''. mone-Ø-t-Ø Latin warn-PRS.IND-3.SG-ACT warns The zero symbol is inserted at that position in the morphological template where an overt morph of the same category C would appear. The same goes for the gloss in cases #b and #c.
A zero morph with function V can be posited only if there could be an overt allomorph of V or at least an overt morph of category C. There are no separate zeros for present and indicative in '' to indicate that tense and mood are coded cumulatively in one morph.
All of these glosses are formally correct. The choice among them is not a matter of appropriate glossing, but of morphological theory and analysis. For interlinear glossing, only the general rule Rule 3 is relevant.
For the possiblity of a zero gloss, i.e. the symbol Ø used as a gloss, s. the section on submorphemic units.
1 A zero morph is a zero allomorph alternating with overt allomorphs of the same morpheme. A zero morpheme is a morpheme always represented by zero. All of the examples given are zero morphemes.