Jitter
Jitter is variation in latency over time: packets arriving with uneven spacing instead of a steady rhythm.
Why it matters
High jitter shows up as stutter, robotic voice, or rubber-banding in games—even if average speed looks fine.
Example in UK broadband
On a video call, steady 40 ms delay is usable; delay that swings between 20 ms and 120 ms breaks lip-sync and causes dropouts. Wi‑Fi congestion and bufferbloat often worsen jitter.