Tenseless or present-tense copulative expressions connecting nouns are more likely to vary diachronically between zero and overt morphemic marking than other copulative expressions or existential or auxiliary expressions. On the one hand, the N1 is N2 construction is the most likely place for optional omission and eventual full deletion, and, on the other hand, when the language has a zero copula, this same construction is the most likely place for the appearance of a new copulative marker.
Standardized
Tenseless or present-tense copulative expressions connecting nouns are more likely to vary diachronically between zero and overt morphemic marking than other copulative expressions or existential or auxiliary expressions. On the one hand, the N1 is N2 construction is the most likely place for optional omission and eventual full deletion, and, on the other hand, when the language has a zero copula, this same construction is the most likely place for the appearance of a new copulative marker.
Expressed as an achronic implication:IF there is a zero copula in tenseless or present-tense nominal clauses where the predicate is a noun, THEN there are zero copulas or auxiliaries also in clauses with other kinds of predicates.However, owing to the second part of the diachronic version of Ferguson’s, it should also be possible for a (new) overt copula to exist only in N is N clauses.See ##1978, 1981.
Expressed as an achronic implication:IF there is a zero copula in tenseless or present-tense nominal clauses where the predicate is a noun, THEN there are zero copulas or auxiliaries also in clauses with other kinds of predicates.However, owing to the second part of the diachronic version of Ferguson’s, it should also be possible for a (new) overt copula to exist only in N is N clauses.See ##1978, 1981.