Arguments and Adjuncts

Once phrases are in view, the next question is which elements a predicate must have and which are merely optional. An argument, syntactically, is an item that completes the thought of a predicate. This idea is very hard to separate cleanly from semantics, and there is much specialized work distinguishing a syntactic argument from a semantic one, but that issue can be set aside here. An adjunct, by contrast, is an item that adds additional information to a predicate but is not required to make it a complete thought.

What a verb requires

The verb give makes the contrast concrete. If someone says only Ezra gave, the thought is badly incomplete: What did he give? Who did he give it to? Likewise gave a stuffed animal to a child prompts the question, who gave it? The verb give requires three elements to complete its meaning: someone to give (the giver), something to be given (the thing given), and a recipient. Those are the arguments of give.

Strikingly, these arguments remain present even when they are not pronounced. Asked, "Did everyone give what was required of them?", one can answer, "Yes, we gave." On the surface there is no object and no recipient, yet the sentence is still understood as having all three participants. The giver, the thing given, and the recipient are all still there. Even when they are absent phonetically, they are present logically: the logical form of give always includes its three components.

Adjuncts

Adjuncts behave differently. In Ezra gave his stuffed animal to a child (at 3 p.m.) (on Wednesday), the bracketed phrases at 3 p.m. and on Wednesday are adjuncts, not arguments. The sentence Ezra gave his stuffed animal to a child is already a complete thought; one can freely add at 3 p.m., on Wednesday, in his room, and more. These further specify when, where, and how the event took place, but they do not complete the thought of the verb.

This yields a key asymmetry. A verb requires a fixed, limited number of arguments, but it permits, in principle, an unlimited number of adjuncts. There is no grammatical constraint on how many adjuncts a sentence can have — human processing imposes limits, but the syntax, in theory, does not.

Interpretation and hard cases

Arguments and adjuncts are also interpreted differently. An argument is typically affected by the verb in some specific way — the stuffed animal is what gets given — and the standard tool for describing such roles is theta roles. Adjuncts instead specify circumstances of the event and are less necessary for describing what actually happened. Telling the two apart is not always easy: stuffed animal is a hard case — is it a compound word, or is stuffed an adjunct to animal? Grasso analyzes it as a compound, but the example shows why careful definitions and diagnostic tests matter.