> The syntactical study of a language is the study of the expressions of the language and the relations among them *without regard* to the possible interpretations or 'meaning' of these expressions.
Syntax is talking about the order and placement of propositions relative to connectives and what constitutes a well-formed expression in these terms. Semantics is about what the connectives mean, in other words: truth-functions and truth-values and not just placement and order.
## Formal specification of the syntax of the language of Sentential Logic
### Vocabulary
Sentences in SL are capitalised Roman letters (non-bold) with or without natural number subscripts. We may call these sentence letters. For example:
````plain
P, Q, R...P1, Q1, R1...
````
The connectives of SL are the five truth-functional connectives:
````
~, &, v, ⊃, ≡
````
The punctuation marks of SL consist in the left and right parentheses:
````
( )
````
### Grammar
1. Every sentence letter is a sentence.
1. If **P** is a sentence then **~P** is a sentence.
1. If **P** and **Q** are sentences, then **(P & Q)** is a sentence
1. If **P** and **Q** are sentences, then **(P v Q)** is a sentence
1. If **P** and **Q** are sentences, then **(P ⊃ Q)** is a sentence
1. If **P** and **Q** are sentences, then **(P ≡ Q)** is a sentence
1. Nothing is a sentence unless it can be formed by repeated application of clauses 1-6
### Additional syntactic concepts
We also distinguish:
* the **main connective**
* **immediate sentential components**
* **sentential components**
* **atomic components**
These definitions provide a formal specification of the concepts of atomic and molecular sentences *introduced earlier*.
1. If **P** is an atomic sentence, **P** contains no connectives and hence does not have a main connective. **P** has no immediate sentential components.
1. If **P** is of the form **~Q** where **Q** is a sentence, then the main connective of **P** is the tilde that occurs before **Q** and **Q** is the immediate sentential component of **P**.
1. If P is of the form:
1.**Q & R**
1.**Q v R**
1.**Q ⊃ R**
1.**Q ≡ R**
where **Q** and **R** are sentences, then the main connective of **P** is the connective that occurs between **Q** and **R** and **Q** and **R** are the immediate sentential components of **P**.
