A well-formed formula is a syntactically correct arrangement of symbols, i.e.,

a. Upper case letters

b. Operators

c. Logical punctuation marks (parentheses, brackets, braces, etc.)

d. Logical variables (p,q,r,s,etc.)

a. Statement Form: A statement form is a tautology iff it is true for every substitution instance (i.e., the final colum of its truth table has only T truth values).

b. Statement: A statement is a tautology iff it is a substitution instance of a tautologous form. 

Statement Form: A statement form is a self-contradiction iff it is false for every substitution instance (i.e., the final colum of its truth table has only F truth values).

b. Statement: A statement is a self-contradiction iff it is a substitution instance of a self-contradictory form.

a. Statement Form: A statment form is a contingency iff it is true for at lesat one substitution instance and false for at least one substitution instance (i.e., the final column of its truth table has at least one T truth value and at least one F truth value).

b. Statement: A statement is a contingency iff it is a substitution instance of a contingent form

a. Statement Forms: Two statement forms are logically equivalent iff the two final columns of their joint truth table are identical

b. Statements: Two statements are logically equivalent iff they are substitution instances of logically equivalent forms.

a. Statement Forms: Two statement forms are inconsistent iff there is no line in the final columns of their joint truth table on which both forms have the T truth value.

b. Statements: Two statements are inconsistent iff they are substitution instances of inconsistent forms.

a. Statement Forms: Two statement forms are consistent iff there is at least one line in the final columns of their joint truth table on which both forms have the T truth value.

b. Statements: Two statements are consistent iff they are substitution instances of consistent forms.

a. Statement Forms: One statement form logically implies another form iff there is no line in the final columns of their joint truth table on which the first has the T truth value, while the second has the F truth value.

b. Statements: One statement logically implies another statement iff they are substitution instances of implicative forms.

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b.