Psalm 78/Notes/Lexical.V. 47.526706
From Psalms: Layer by Layer
v. 47 –The word גֶּפֶן is always found in the singular, even when modified by plural quantifiers (see, e.g., אֶ֥לֶף גֶּ֖פֶן "a thousand vines" in Isa 7:23). Since the form is ambiguous between a singular and plural reference, context is determinative. In the present case, the denotation of all the vines of Egypt, and the parallel with the plural וְ֝שִׁקְמוֹתָ֗ם "and their sycamore trees" support the plural interpretation (see also Jerome's Hebr., Syr., and TgPs).