What is the difference between an anomalous narration and the addition of a trustworthy narrator?

The Shaykh : ...and the anomalous narration. Between them there is a relationship of generality and specificity, for not every addition by a trustworthy narrator is accepted.

Another questioner: Peace be upon you.

The Shaykh : And upon you be peace, and the mercy of Allah and His blessings.
This is because the definition of an anomalous narration according to them is: an addition by a trustworthy narrator that contradicts someone who is more trustworthy than him or has a larger number of narrators. Once we know this rule and this criterion, we then understand what they mean when they say: "The addition of a trustworthy narrator is accepted." That is, when a hadith comes from two trustworthy narrators who are equal in terms of justice, trustworthiness, precision, and memorization, and one of them adds something to the other, this addition is accepted, whether it is in the chain of narration or in the text. However, if the one who added it is less precise in memorization than the other trustworthy narrator who did not include it, this addition becomes anomalous. More specifically, if the one who added it contradicts a trustworthy narrator, and if he contradicts someone who is more precise in memorization, his addition becomes anomalous. If he contradicts someone who has a larger number of narrators and is more precise in memorization—and peace and mercy of Allah be upon you—then the hadith becomes anomalous.
The term "anomalous" is used specifically for what a trustworthy narrator narrates alone, whose hadith is usually authentic. However, if his hadith is usually below the level of authentic—that is, good—and then he contradicts someone who is more trustworthy, his addition becomes denounced. Thus, the denounced corresponds to the anomalous, and the anomalous corresponds to the denounced. If it is said that this is an anomalous hadith, it must occur to the student of knowledge that the speaker—if he is knowledgeable in this science—means that the trustworthy narrator narrated it alone, contradicting someone who is more trustworthy than him or has a larger number of narrators. But if it is said that this is a denounced hadith, that usually or sometimes means that he contradicted someone who is more precise in memorization; that is, the hadith of the more precise narrator is good, let alone if he is trustworthy. However, the one who contradicted is weak; his hadith is weak according to the rule and the standard. If this weak narrator contradicts someone who is more precise in memorization, whether the more precise narrator's hadith is at the level of good or authentic, then his hadith becomes denounced. But here, the term "denounced" has another usage among some scholars of hadith, such as the Imam of the Sunnah, Imam Ahmad (may Allah have mercy on him). He uses the term "denounced" for a hadith that a weak narrator narrated alone, without the weak narrator contradicting someone who is more trustworthy. Therefore, it is not a condition for some of them, like Imam Ahmad, that the narrator of the denounced hadith, who is weak, must have contradicted someone who is more trustworthy.
The point is that there are two usages for the term "denounced," whereas for "anomalous" there is only one usage. This clarifies the difference between an anomalous hadith and their statement: "The addition of a trustworthy narrator is accepted."