Propositions are the basic units of logic and language that can be either true or false. There are several types of propositions: - Categorical propositions make a claim about a subject and predicate, and can be universal, particular, affirmative, or negative. - Hypothetical propositions state conditions and possibilities using "if-then" clauses, with the antecedent as the condition and consequent as the possibility. - Disjunctive propositions present alternatives using "either-or", and can be strict if the possibilities exclude each other, or broad if the possibilities can both occur. - Conjunctive propositions combine possibilities using "and" that cannot both be true simultaneously