Inconsistency, n.; pl. Inconsistencies.
Etymology: [Cf. F. inconsistance.]
1. The quality or state of being inconsistent; discordance in respect to sentiment or action; such contrariety between two things that both can not exist or be true together; disagreement; incompatibility. There is a perfect inconsistency between that which is of debt and that which is of free gift. South.
2. Absurdity in argument ore narration; incoherence or irreconcilability in the parts of a statement, argument, or narration; that which is inconsistent. If a man would register all his opinions upon love, politics, religion, and learning, what a bundle of inconsistencies and contradictions would appear at last! Swift.
3. Want of stability or uniformity; unsteadiness; changeableness; variableness. Mutability of temper, and inconsistency with ourselves, is the greatest weakness of human nature. Addison.
Shades of meaning
Fernald has no entry of its own for inconsistency; he lists it under difference.
He lists it without comment; the entries above explain its neighbors.