# What does _ mean in Prolog?

**means**"any term". Unlike other variables, the underscore

**does**not represent the same value everywhere it occurs within a predicate

**definition**. A compound term is composed of an atom called a "functor" and a number of "arguments", which are again terms.

Also to know is, what does + mean in Prolog?

[ISO]**+** :Goal. True if'Goal' cannot be proven (mnemonic: + refers to provable and the backslash ( ) is normally used to indicate negation in **Prolog**).

Subsequently, question is, what is a term in Prolog? All **Prolog** data structures are called terms. A **term** is either: A constant, which can be either an atom or a number. A variable. A compound **term**.

Similarly, what is functor in Prolog?

**functor**, **functor In Prolog**, the word **functor** is used to refer to the atom at the start of a structure, along with its arity, that is, the number of arguments it takes. For example, in likes(mary, pizza) , likes/2 is the **functor**.

What is a Prolog predicate?

**Predicates**. Each **predicate** has a name, and zero or more arguments. The **predicate** name is a **Prolog** atom. Each argument is an arbitrary **Prolog** term. The clauses that constitute a **predicate** denote logical alternatives: If any clause is true, then the whole **predicate** is true.