Link velocity
Link velocity is the rate at which a site gains (or loses) backlinks over time, measured per week or month.
Link velocity describes the pace of your link acquisition. It is not a single number you optimize so much as a trend you watch: a site earning a steady, gradually growing stream of links looks very different from one that suddenly acquires hundreds in a week.
It matters because unnatural spikes can look like manipulation. A brand-new site that gains thousands of links overnight, or a sudden burst of exact match anchor links, fits the pattern of a paid or automated campaign and can attract scrutiny. Earning links at a rate that matches your content output and PR activity is the safer, more durable path.
Be careful with the myth of a fixed safe velocity. There is no magic number, and genuine virality, a digital pr hit, or a linkbait asset can legitimately produce a large, fast spike. Context is what matters: a spike backed by real coverage from quality domains is fine, whereas the same spike from a network of thin sites is not.