Parashat Toladot opens as follows: "These are the 'toladot' of Yitzchak: Avraham begot Yitzchak."
Although the term "toladot" generally refers to offspring, many translators and commentators prefer to translate this phrase as "This is the story of Yitzchak..." The reason is clear: if the verse opens, "These are the offspring of Yitzchak," then we expect the verse to continue with Yitzchak's children, not the already-known fact that Avraham was Yitzchak's father!