Amplify vs App - What's the difference?

As a verb amplify

is to render larger, more extended, or more intense, and the like;—used especially of loudspeakers, telescopes, microscopes, etc.

actinobacllus pleuropneumoniae.

(en-verb)

To render larger, more extended, or more intense, and the like;—used especially of loudspeakers, telescopes, microscopes, etc.

(rhetorical) To enlarge by addition or discussion; to treat copiously by adding particulars, illustrations, etc.; to expand; to make much of.

* Dryden

Troilus and Cressida was written by a Lombard author, but much amplified by our English translator.

To increase the amplitude of something, especially of an electric current.

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(en-plural noun)