Oratory, n.
Etymology: [L. oratoria (sc. ars) the oratorical art.]
The art of an orator; the art of public speaking in an eloquent or effective manner; the exercise of rhetorical skill in oral discourse; eloquence. "The oratory of Greece and Rome." Milton. When a world of men Could not prevail with all their oratory. Shak.
1 other Webster entry under this spelling
Oratory, n.; pl. Oratories.
A place of orisons, or prayer; especially, a chapel or small room set apart for private devotions. An oratory [temple] . . . in worship of Dian. Chaucer. Do not omit thy prayers for want of a good oratory, or place to pray in. Jer. Taylor. Fathers of the Oratory (R. C. Ch.), a society of priests founded by St. Philip Neri, living in community, and not bound by a special vow. The members are called also oratorians.
Shades of meaning
Fernald has no entry of its own for oratory; he lists it under speech.
He lists it without comment; the entries above explain its neighbors.