The restriction of a deductive system $\text{L}$ by considering only formulae of some special type. More precisely, a fragment of $\text{L}$ is the logic determined by the restriction of $\text{L}$’s consequence relation to a proper subset of the language of $\text{L}$. Fragments may be taken by considering only formulae with certain connectives, e.g., the implicational or positive fragments of a logic $\text{L}$ with a conditional connective $\to$ or negation $\neg$ range over only those formulae in which no connective but $\to$ appears or formulae containing no instance $\neg$, respectively. In systems $\text{L}$ with an intensional implication connective $\to$, the first-degree fragment of $\text{L}$ (frequently symbolized as ${\text{L}}_{\text{fde}}$) is the collection of all first-degree theorems of $\text{L}$, i.e., those theorems of the form $\phi \to \psi$ where $\to$ appears in neither $\phi$ nor $\psi$.