Fealty
An oath of fealty, from the Latin fidelitas (faithfulness), is a pledge of allegiance of one person to another.
Fidelity
Fidelity is the quality of faithfulness or loyalty. Its original meaning regarded duty in a broader sense than the related concept of fealty. Both derive from the Latin word fidēlis, meaning “faithful or loyal”. In the City of London financial markets it has traditionally been used in the sense encompassed in the motto “My word is my bond”.
Fealty (noun)
Fidelity to one’s lord or master; the feudal obligation by which the tenant or vassal was bound to be faithful to his lord
“fidelity|allegiance|faithfulness”
Fealty (noun)
The oath by which this obligation was assumed.
Fidelity (noun)
Faithfulness to one’s duties.
“the fidelity of the civil servants”
Fidelity (noun)
Loyalty to one’s spouse or partner, including abstention from extramarital affairs.
Fidelity (noun)
Accuracy, or exact correspondence to some given quality or fact.
Fidelity (noun)
The degree to which a system accurately reproduces an input.
Fealty (noun)
a feudal tenant’s or vassal’s sworn loyalty to a lord
“they owed fealty to the Earl rather than the King”
Fealty (noun)
formal acknowledgement of loyalty to a lord
“a property for which she did fealty”