Generalisation: Reading of "φ(ωj, ..., ωk" (Grice in Davidson/Hintikka, p. 125

That second rule in the glossary of the natural deduction contains a sub-clause which generalises over 'alpha' now to cover any variable, for which Grice uses omega.

Thus:

"φ(ω_j, ..., ω_k"

will be read as

"a formula "φ(ω_j, ..., ω_k" where ""ω" denotes a variable".