symbolic units that connect a linguistic form with meaning
In other words, what do speakers of English know in order to produce utterances that other speakers will understand?
The theory of construction grammar postulates that lexical items and syntactic patterns are symbolic, meaningful units. Also, the syntax used contributes to the meaning of what's said.
This topic can also cover mixed constructions. Example: "Beginning in the winter of 1945, the beginnings of the party began to take root, was the target of much international attention."
This topic can also cover parallel constructions, one or more sentences of similar phrases or clauses with the same grammatical structure.