Health
What is Heart rate variability (HRV)?
Variation in time between heartbeats; SDNN is a common summary metric in consumer apps.
Learn this term every day on iPhone.
One hand-written term. A real workplace example. Thirty seconds before your day gets loud.
In real work
Lower HRV after poor sleep is common; trends matter more than one reading.
How is this different from Googling it?
Google gives a definition. Prompthaus pairs each term with how it shows up in standups, PRs, prompts, and design reviews—then quizzes you until the word sticks. One term a day on iPhone.